although I've never been to the parks during "gay days" I can only assume that there will not be any "behavior" you don't want your kids to see, any more than heterosexual behavior. most people do not go overboard on PDA's(public displays of affection), no matter the sexual orientation. my hubby and I have one couple we know who go way overboard on PDAs and they are a straight couple (sometimes, it's, like, "get a room!", ) but I know a gay couple who never hardly ever touch in public. most people realize it is a family atmosphere and act accordingly, gay or staight.
as far as crowds go, it might be a little more crowded, but considering the next week schools let out, I'd rather not go in the typical "summer" months, when most schools are out, and the crowds really build up.
anytime there is a "special" days offered, you can count on a little more crowding. I always wanted to go for super soap weekend (I'm an "all My children" fanatic") but I KNOW MGM that day will be crazy. star wars weekend, food and wine festival, etc. we love may, flower and garden festival. the week of joy (christian music) I hear can be crowded too.
I would go whenever it fits your schedule, but try to stay away from spring break, summer months, and the week between christmas and new years, if possible