We have been wearing Crocs to the parks for several years now. Of course, we live in Boulder, CO where the guys who developed Crocs live and work, so we have had Crocs here for longer than the rest of the country. Our swim teams around here test marketed many of the prototypes

It is fun to see what a phenom they have become! The first time we wore them to Universal, people looked at us like we were absolutely nuts in these ugly plastic clogs. Now we see them all over the place.
The Crocs are supposed to be a bit big and sloshy. As long as your foot fits in the footbed, the sides will feel big. That is the comfort. If you want the traditional look Crocs - try the Caymans. They have a narrower foot bed than the Beach Crocs. Most of the Crocs you find at Dillards, etc are Beach, so ask around to make sure you are trying on Caymans. Also, make sure you try on real crocs. The cheap imitations don't have the specially designed foot bed that the real crocs do, so they don't fit like the real ones.
And you can't have a better shoe for the water rides, as they don't get squishy and dry immediately.
Last July, we took our neices with us for a 10 day trip. One early morning, we were walking through Amity and one of the game people yelled out to us that we looked like a box of crayons. I didn't get it at first, but then I looked down - 8 people - 8 different colors of crocs. And the bright colors to boot. We were a sight I have to admit.
I have the Athens (as well as Beach, Caymans and Niles) and I don't think I could walk a whole day in the parks in the Athens. They just don't have the same comfort of the others. I love my Athens and wear them everyday here, but I definitely prefer the Beach or Caymans for all day walking.
Check the Community Board - there is a HUGE thread on Crocs. Lots of great tips on where to get them, sizing, etc.