You should have the fathers of the bride and groom, any brothers and the groom arrive about 30-45 minutes toward the end of the party to say hello and load the car(s) with the bags and boxes of gifts you (and the groom) received.
Another idea is to get the groom to arrive earlier and take part in a game - like the newlywed game - during the shower. I like this idea because it's more fun when you hear the groom's responses live and you can see the couple interact with each other.
