Also, talk with that other fella. Find out what he is using to shoot. If he is using flash and standard zoom, you can go to town with the 50/1.8 and shoot the creative photojournalistic shots.
You are not the only photographer.. so the pressure's off. Just relac and enjoy shooting. No worries if the pics are no good, since the couple is the one who are trying to save some dough instead of paying someone to get it done right. I mean... for my own ROM, I paid $150 only but then again, my ROM was a 15min affair.