We have brought...
Individual bags of goldfish crackers
A box of cheerios & baggies (my kids still like to snack on these)
Peanut butter crackers - for times when they haven't eaten much and I want to give them a little more than just crackers or cereal.
I placed an order with Garden Grocer so that we had some healthy snacks for the room too - applesauce, yogurt, fruit, etc.
There are plenty of good choices around the parks too - fresh fruit (whole and cut), apples & dip, veggie sticks and dip, yogurt, etc.