My daugther - then 4 - was and still is a picky eater.
She LOVED the "Cruncheerios" cereal. They are similar to Cheerios - just a little crunchier.
We started getting room service to bring two or three little boxes with milk to the room. Then, if she needed a little snack, she could have them plain or with milk. I didn't discover this until late into the second day of our 4 day, but on our 7 day in May, I am going to get them to deliver some on the first day as a back up!
Have fun on your trip!