we pack a small bag for each of them (2 & 4) with goodies,
stickers!! and a sticker book to put them in
snacks, raisins, bananas or banana chips, hi c boxes, pretzels, pb&j sandwhiches, those small cereal boxes, etc..
a small can of playdough for each of them
a pad of paper like a small notebook and some crayons
thier favorite stuffed animal and blankie
and usually a couple match box cars or airplanes to play with
they do most if not all of this on the tray tables..
they'll be just fine

good luck !