Thanks for the ideas guys.
Just to the left of the shot is the main church entrance, which has a very "oldy worldy", tudor-like wooden framed entrance. I think I will try to get the main formal shots of folk stood in front of that and the main church itself, and then use the bench for the smaller group shots, perhaps - especially the one's with kiddies.
The issue regarding the headstones - I'd considered this but felt that the group size combined with shallow DOF (they are quite a way back from the tree) would probably help mask them. I think when photographing in a church yard these are always going to be a feature, to some extent, aren't they? We have to just do our best to ensure they're not prominent. Just my view.