My niece insisted on wearing foam flip flops a few years ago. She was very uncomfortable at the end of the day, and the plastic strap broke. At that point she HAD to go back to the room.
Not only is there no arch support, but also you have to worry about people stepping on your toes and strollers and uneven pavement (i.e. smashing your toes into concrete.) Flip flops are great to wear to the pool, and great to put on just before a ride like Kali River rapids, but I wouldn't wear them all day. If your toes get smashed, you'll be unable to enjoy the rest of your trip!
On the other hand, there were lots of people wearing
crocs and more expensive sandals. (mind, you'll also se stupid people wearing high heels to the parks too!) I would say wearing more expensive sandals - like the kind with cork/arch support is a great idea! I really like not having socks on my feet the entire time, and I also like the look of sandals with certian outfits. If you have the kind of sandals with cork bottoms, not only will you get cushioning and arch support, but the added height gives much better protection from mishaps. Mine are all black from Clarks. I don't know that they have the same style out this year.
Having said all that, I still couldn't wear sandals the entire time. I think it's best to trade shoes periodically. If nothing else, it's good to let your shoes air out a bit, so you don't get fungal problems.