We had registry office do at 2.00pm, then went to local Tapas Bar (had it to ourselves) for meal with family and close friends - about 40 of us. Then we brought younger kids home and babysitter took over, we went back out and had a big party with everyone else. It was lovely having the kids at the ceremony, and great having them there for the meal but I wouldn't have wanted them there in the evening for the party. It was definately time to relax and let our hair down without fretting about DCs.
Congratulations, by the way - hope it all goes well.