OMG! I've been thinking exactly the same for my brothers wedding. So exciting!
I would of suggested Queen but i think they know i'm going to suggest it anyway!
It's difficult choosing because you need to find music suited to all tastes.
Why not try something Big Band or Jazzy or swing.. like, one of my favourites, Frank Sinatra. Everyone has a liking to his songs.
Or maybe something with impact that fits the occasion.
What artists does your mother like?
"It’s not often we play in daylight, and I fucking well wish we did before, I can see you all now. And there are some beauties here tonight, I can tell you!" ;)