What you include will totally depend on budget, personality, and space. PP and I have some of the same ideas! I suggest including something from the following groupings of snacks, water bottle (pre-wash it so it's ready), activity for plane, clothing, plush of some sort. So here is the full list of options:
* snacks! so key for the plane and think of things that aren't too sugary but are filling as well as some treats -- stuff like dry cheerios. You can consider getting a lunchbox and putting them all in there for easy location and access. Make sure you have extra ziplocs if any leftovers need to be stashed
* Disney band aids
* coloring books, crayons, stickers
* water bottle
* stuffed animal
* autograph book or supplies -- you can make a personalized one via the Creative DISigns board below or go functional and fun with a pillowcase, fabric markers and embroidery hoop (holds it taut to autograph)
* a DIY coupon book! My new fav from the Creative DISigns board as well -- personalized coupons for things like cupcake, popcorn, special treat, pick the next ride, certain rides like Kilimanjaro safari and shows like Enchanted Tales with Belle, coin for Snow White's fountain, and "take a break" coupon.
* take a mini M&Ms tube and fill with 2 quarters and a penny and repeat. Perfect for pressed pennies!
* sunglasses, hat, mini mister fan (you'll need it!) -- they sell some on line that are carabiner clip ones