Best way to take these shots?

Sorry I don't have any pics on mine since I'm on a different computer. I've noticed a lot of wedding shots... where the couple is lined up within a depth of field... the wife is further back from the husband and the bridesmaids and groomsman are further back and blurred out.

When you're on the fly, how do you guys best determine what apperture to use to acheive a good enough distance to keep the husband and wife in focus and the rest of the line down blurred?

I'm thinking I'd shoot wide open but then the husband lets say will be completely in focus but the wife may be partially in focus the part of her body that's leaning further away would be out of focus...

Thanks