If so, here is our checklist that makes us at least feel prepared and get to our destination pretty successfully (which means we can actually enjoy said destination!).
And we have used ALL of the items listed below for the reasons listed below... I am not just being a worrywart!
Travel - Airport/Flight/Car Trip -
Snacks. Bring your sippy cup for filling with water once through security, and refill it whenever possible. Flights are long, and you never know when you will get delayed or hit traffic on the road.
Also pack favorite snacks. For us that means cheese, fig newtons, goldfish, raisins/dried fruit, PBJs (still taste good smushed). Throw in an apple or other hearty (as in you won't find it smushed at the bottom of the bag later) whole fruit/vegetable for good measure (apples, baggie of grapes or melon chunks, carrots, snap peas). Pack twice as many as you think you'll need because you may get delayed, or hungry yourself, or they may just be the thing that keeps your toddler from melting down. We often enjoy Delta's fruit and cheese plate... but you may not want to wait - or pay - for it. Consider milk boxes because milk on a plane or in an airport, or even at your destination, may be scarce, and these don't have to be refrigerated.
Toys. Bring the iPad if you have it, and preload it with some of your toddlers favorite videos, games and apps if you can. Spring for the internet on the plane if its a long flight, and watch YouTube videos. Pack toddler headphones if you have them, too. Not everyone loves Elmo for the 18th time.
Play doh - my son got some mini cans of play doh as birthday favors and valentines. They are the only play doh we own, and works pretty well on an airplane tray. You could also make your own and pack it in a sandwich baggie.
Toys with few parts - pick some of your kids favorites that are small enough to be packed in a diaper bag/carry on and have few parts so you don't lose them or spend a lot of time fixing them. Polly pockets are out. Travel magna doodles are in (I think my mom us got a much less fancy version for my son's Easter basket from a dollar store and it has been a fantastic toy for travel and restaurants for over almost a year!).
Restaurant crayon pack and coloring book - you know that 4-pack of crayons you get every time you go to your favorite restaurant? Save a couple of them (my husband is cringing) and throw one in your travel bag. You won't care if you lose them and your toddler won't care that there's not a full 8 or 64. Throw in a coloring book for good measure if you have it. If not, a pad of paper, or use in flight napkins if you have to. Coloring is a 'together' activity!
Other books - besides regular entertainment, books are handy to have to protect nap routines in-flight AND to have at your destination for bedtime, too.
Cars or the like - for hours of driving around airports, rest stops, gas stations, grandma's, on armrests, practicing colors. I hear girls like playing with cars, too, right?
A new Toy - or book. Some people even wrap them. But something novel always cheers up a little one. Doesn't have to be big or flashy or expensive. Just different from the regular stuff he plays with.
Blanket - planes are chilly! Plus a blanket can cover a dirty floor for your little one to get some tummy time. Or it can be a sunshade on the plan or in the car. Or it can be another toy. Our plane was delayed HOURS on our last trip but our toddler thought it was fun to lay across some seats at our terminal and cover himself up and then 'wake up' over and over. We like an Aden & Anais because its big, but packs small and is plenty warm.
Clothes I dress myself and the toddler in convertible pants (the kind that can roll up and be buttoned there) because it can be hot in the airport and cold on the plane/car, etc. Pack at least two changes of clothes for the kid, and at least one for yourself. $h!t happens.
Diapers - 'cause of all that water you've been offering. And you will need more than usual because things just happen... but also because you'll change one last diaper before strapping the kid back in the carseat, or boarding the plane, which will be 5 minutes before they decide to poo... and again... you never know about delays or traffic. We use cloth, but we always carry at least one disposable on top of double the diapers we would normally go through in the same amount of time. AND WIPES. FOR EVERYTHING. Hand sanitizer, too.
Your child's suitcase - We usually bring our son's suitcase as one of our carry on's for the plane. Our luggage has been lost recently, and we think its most important to have his stuff in that event. Also, its handy in case you thought my diaper and clothing estimates were over the top, to have more wardrobe and diapers to fall back on. :)
Trunki - Also fun for a toddler to scoot around in the airport or at Grandma's. Ours only comes out for traveling, so it's a novelty. And we stuff all the toys and the blanket listed above in it! (trunki at Amazon)
Diapers. If you are packing cloth, check with your host ahead of time to see if they mind you using their washer for diapers. They will likely let you, but at least this gives them time to adjust to the idea, if they may privately be thinking, "EW!". Bring your own detergent (I stock up on freebie samples when I make my diaper purchases and pack them just for trips) because its polite, and because they may not have the cloth-diaper-friendly variety.
If you are using disposables (because you won't be able to wash at a hotel, or because you use disposables all the time :) ), consider mailing a box to your destination ahead of time (or ask grandma buy some for you and have them ready), so you dont' have to pack this on the plane or car. And make sure the box contains more than you would usually use... because of Murphy's law. Don't depend on buying some when you get there because who knows when your first opportunity to get to the store will actually be. And you will have used all of your travel stash while traveling. Promise.
Clothes. Suitable for your destination. Will you need a swimsuit (and swim diapers)? Will you need pants? Shorts? A coat and hat? Dress clothes? Special colors for a family portrait? Should you pack that outfit so-and-so gave you that you really never let him wear but she would love to see Junior in? Don't forget socks and suitable shoes.
Toiletries. Toothbrush and toddler toothpaste. The others stuff can probably be subbed in a pinch, but just for completenes: baby wash, lotion, diaper cream, other ointments... and our mini-first aid kit of a thermometer, tylenol, bandaids, and neosporin. Maybe you need vitamins or some other prescription, too?
SUNSCREEN. enough said.
Pack n Play. If you a driving, you may have room for this in the car, but you may also check to see if your host has one or can borrow one for you to use (if your little one still fits in one... ours is too big for our mini-crib, so we are going to try a camping mat -that we already own- in a few weeks... fingers crossed)
Stroller or baby carrier. If you think you'll be out and about a lot. The stroller can be handy for naps on the go... we usually only get an hour tops (and we prefer more like 2 hrs) but its better than nothing if you really can't be home in a bed. A carrier is good for long walks or crowds.
Booster seat. If your child needs one. Grandma keeps one at her house and offers to bring it if we meet at an alternate destination. Just ask your host.
Potty Chair.We are just now starting a potty routine and I don't want to mess it up, so I purchased this travel potty seat recently to test out this weekend... I'll let you know how it goes.
Cups and cutlery. If you are visiting a place that doesn't have kids living there.
Other things to keep in mind:
Try to stay on schedule, even/especially if you've changed time zones. We live on the West Coast and our family on the East, so we operate like teenagers when we visit (staying up late and sleeping in). It so easy to let friends and family lure you into letting the little one stay up 'just one more hour'. Or maybe your extended family is like ours and eats late breakfasts, or skips some meals entirely. I personally have trouble with this, but the poor toddler really can't handle it. So I try to be up front about our 'plans' for the day, and ask ahead of time what friends and family have planned, so we can work in naps (and pre-nap energy expenditure) and meals, too.
Did I leave anything out? What are your travel 'must haves'?