Hi there, Sarah!
I've been hashing out this same thing with my daughter, who will be bringing her infant son to
Walt Disney World in a few weeks. We've looked at the single packets of formula, which make one bottle each, but my daughter is still worried we won't pack enough.
You can absolutely bring the can of formula and the water with you into the park each day. You might want to just tell the security guard when you check in that you have it, just so they know what you've got.
I also can't recommend enough the
Baby Care Centers. Located at each theme park, pretty much anything you might run out of, you may find available to purchase there. They have a variety of formulas, baby wipes, diapers, and baby food and snacks. There are other baby essentials available there, including changing tables, rocking chairs, and even high chairs and seats for older children. You shouldn't have to run back to the resort for anything you've forgotten - check the baby care centers first.
Don't forget the pictures! Use the
Disney PhotoPass photographers to capture those amazing moments of your baby at Walt Disney World. You could even buy
Memory Maker, which will give you unlimited digital downloads of your favorite photos. Oh, the memories you'll make!
Have a wonderful trip, Sarah!
Anna