In general, I aim to travel light, but I've learned over the years that this generally isn't a good strategy as a parent. If anything teaches you the happiness value of preparation, it's parenthood. The right supplies can mean the difference between misery and good cheer.
If you're traveling with a baby, of course you need a whole different set of supplies. My children are ten and four, and now I never go on a trip without at least most of these items:
1. A bag of almonds. These are for me as much as for my children.
2. A bottle of water. (Usually I'm violently opposed to bottled water, but I now concede that it's good to have a bottle when you travel.)
3. Novelty candy. By this, I mean a candy that's odd (e.g., Pop Rocks, candy spray) or takes a long time to eat (candy necklace) or fun in some way (Pez). I save this to whip out if my kids get crabby. Chocolate or anything that can melt is a risky choice.
4. Coloring book and markers, but REMEMBER to make sure that the markers aren't all dried out. Just learned this the hard way. (Spend out! Don't put a dud marker back in the box. A metaphor for life.)
6. Wipes. Not just for babies anymore.
7. Camera. Remember to charge it. Learned that the hard way, too.
8. We finally caved and bought a portable DVD player. This is a great invention. I actually finished Ken Follett's The Pillars of the Earth on the plane while my daughters were transfixed by My Neighbor Totoro.
Irrelevant note to entrepreneurs out there: I think the scratch-n-sniff market has been sorely overlooked. Growing up, my sister had a collection of scratch-n-sniff stickers, and we still have fun going through her big pile. The Sweet Smell of Christmas is one of our favorite picture books. Happiness is a great scratch-n-sniff!
* Interested in starting your own happiness project? If you'd like to take a look at my personal Resolutions Chart, for inspiration, just email me at grubin, then the "at" sign, then gretchenrubin dot com. (Sorry about writing it in that roundabout way; I'm trying to thwart spammers.) Just write "Resolutions Chart" in the subject line.