I guess I'm going to be one of those posts that really doesn't have too many suggestions, but a whole lot of support! (BTW-I'm not bisexual or a lesbian-but I think there is nothing wrong with that lifestyle "choice"~~>Please note the quotation marks!)
Some suggestions? Well, I'd 1st make sure that your audience is willing (how many of those in your college have children? One college I attended had about 80% parents, the one I'm attending now has about 5%). If they are (and that's great!), ask them what they'd like! They may have some great ideas as to what works for their children and what they deem appropriate and inappropriate, etc.
Try to find some type of coloring book or something (regular books would probably be too expensive) that maybe you could reproduce that show all types of couples/races/etc.
Maybe even a mini child's pride parade around campus if you want to make a statement. They could hold little signs or something, have rainbow face paintings, etc. I'd suggest not making anything for little kids too political though.
Definately have some non agenda related activities (BBQ, a clown or juggler, if it's Autumn candy apple making or pumpkin painting/carving/picking-something like that).
Well, best wishes with every thing!
PS-I'd also invite straight couples and their children to really promote acceptance. I know that at least a few of them would be into it, and the more the merrier as long as the object is the same.