My youngest DD loves dogs and when she was little, I had bought about five or six little plastic dogs that I kept in one of her purses in the van. These little dogs were only about an inch tall. Anyway, the only time the purse with puppies came out was at a restaurant. They entertained her for hours!!!
Another "game" we played with all of the girls when they were younger was with the sugar packets. I'd give them 2 or three of the pink, blue, yellow, white, and/or brown packets. She'd stack them, or sort them by color (either all the pinks together, all the blues, etc, or a pink, blue, yellow, pink, blue, yellow, etc)
I also found, with my girls, that I would either let them sit on my lap or in the booth with me for a little while. Then put them in the high chair. Sometimes, they just got tired of being in the highchair.
Have a great trip!!!!