You'll see everything from shorts and t-shirts to thongs, just like any other time of the year!
Seriously, there will be a few people who "dress up" -- I remember one remarkable get-up that was red vinyl, with high heeled platform shoes and a dog collar, and all I could think was, "Red vinyl on a sunny June day ... THAT won't last long." But that was definitely the exception, not the rule. You're more likely to see questionable clothing and a lot of bared skin when the South Americans are in town than you are during Gay Days. (Nothing against South Americans, but they do tend to bare a lot more skin than their neighbors up north.)
You'll see a LOT of red t-shirts (the "official" color of the day), and probably a few drag queens (who may or may not be apparent). Other than that, it'll look like a normal day at the parks. All of the Gay Days participants are there to enjoy the parks too -- they know that comfort is key, and they're not going to do the outlandish costumes if they want to have fun.
As for manner ... you'll see lots of same-sex hand-holding, and probably some kissing. I've seen more public displays of affection by high schoolers than by Gay Days participants, though. In fact, the only times I've actually seen people flat-out making out in the parks has been heterosexual couples! If you end up on Small World or something like that with a bunch of "red-shirts," you'll probably have to endure them all singing along for the whole ride, and like any large group (family reunion, cheerleaders, etc), there will be lots of squealing and hugging and all of that as they see each other from opposite ends of the parks!
Many guests who happen to be there during Gay Days don't even notice it, so unless you go in looking for specific behavior, you probably won't see anything unusual. I would NOT, however, recommend taking your kids to Pleasure Island ....
