idea
You could number each girl gift 1 - 8?? and each boy gift 1 - 8?? or whatever. Then have the kids each pick a number, then they get the corresponding gift. If they get their own gift, you could do a quick change before they all open.
Make sure you have some extra boy and girl gifts just in case someone doesn't bring one. I'd hate for someone to be left out.
I can remember doing this once in 4th grade but I definately couldn't do it with my class. I teach in a poor rural community.