I've done it.
Take a look at 2-3 pro wedding albums - there are several "stock" shots you need to get:
Bridal party together at ceremony - easier to do in low-key ceremony
Bride & groom together
Bride & parents
Groom & parents
It's all pretty formulaic - just think it through ahead of time, make a list, and do it. Just make sure they understand that an amateur family member will not shoot like a pro. The disposable camera idea works well too - a lot of people like the random snaps as much as the pro shots.
This is the Pub. Leave common sense at the door.