Okay, here's the deal.
Many weeks ago my H and I arranged for friends (two couples) to come to ours for dinner and stay the night at the beginning of october. We live 30 mins drive from town where one couple lives. The other couple live in another town altogether, about 2.5 hours drive away. It's a bit of a big deal because we haven't seen each other for about a year and have been trying to get together for ages but giving birth and having a new baby has rather got in the way.
My SIL has just announced that she is going to have her daughter christened on the same day (ie, in a couple of weeks). Obviously we want to go to the christening which is around lunchtime but then she's having everyone back to hers afterwards at 3pm. I don't know how long we should stay before we leave to go home and prepare dinner/have our guests arrive - I haven't discussed with our guests yet what time they should come, but I know that the couple who live 2.5 hours away were thinking of getting here at about 3pm (but I guess I could ask them to go to the other couple first and come to ours later). We live 30 mins drive from my SIL so there is that to take into account too.
What's an acceptable length of time to stay at my SILs for after the christening in these circumstances?