The first dance is often a scary moment for couples. If you're planning a first dance - awesome! I think they're great and they're also a nice way to phase from the formal reception, to the 'get down and party' part of the wedding. When you're dancing with your new partner, there will come a time when you want others to join in. Before your dance, talk to your bridal party and tell them the moment when you want them to flood the dance floor. This will also cue the rest of the guests to come and dance too.
Another idea is to tell the DJ to cue up 4 really catchy songs in a row after your first dance to really get people in the mood (you can't beat the B52's Love Shack). And don't plan anything official after this stage of the wedding. No cake cutting, no speeches, just fun :)