A must stop before staying at the surrounding hotels for necessities such as water, soda, snacks, sunscreen etc. In addition they have a whole section for souvenirs. They don't have the normal Walgreen sales but beats sundry store prices.
I suggest planning a pit stop around this store for a cold drink or even an Icee in 6 flavors.
They also had a whole section for photo developing.
We stopped twice over 2 days and both times although they were busy it was still quick.