People will always appreciate a good picture, and some will always believe that a fast picture with equipment technical enough (we all know that if the pictures aren't good we need a newer lens, right?). With the passing of time the good pictures will be more important and the crappy instant ones will vanish from memory.
I rarely do weddings but when I do I try to scout the place in advance and plan the pictures ahead. There will be a crowd in your way so a small step ladder can be nice to have. You can also bring a camera that stuns the crowd and leave you room to work. A beautiful 8x10 field camera does the trick every time. No-one gets in the way of the shot and I have everybodies attention (you will however be photographed and sent across the net perhaps more than the happy couple but you will have to live with that).

Perhaps I found it strange in your story that so many people were there to witness the proposal. If you knew about it in advance and they didn't they should hardly have time to react before the question was asked and answered.