In MGM isnt the fire hydrant still there that squirts in the City looking area? When we go to DL we always stop with our little ones to get soaked. It makes them happier I think. Like someone said my DH wears swim shorts with a tank that day, and his sandals that can get wet. My daughters wear swinsuits under their clothing. I have NEVER made them wear swim diapers because they cant get that wet. They can get soaked, but its not like these are standing water areas. At most the diaper gets a tiny bit wet, but not like they would if they were in a pool. I just change the diaper when they are done, and take off the swimsuit and put the clothing back on..
Be warned...In DL they REQUIRED kids to keep shoes on in these areas. So either wears shoes that can get wet, or bring water sandals.