Let kids be kids. At this stage they need to learn the basics . . . be nice, don't hit, wash your hands, and so on. Trying to introduce that it's okay for a "Fred" to choose to go to a prom in a dress isn't for this age group. Let them learn the basics first; it's okay that little boys can be different than little girls . . . . leave the "choosing something different" to the young adult stage instead of trying to introduce it into a program for toddlers this young.