D5100 good enough for 2nd shooter at wedding?

My wife and I recently started shooting weddings.  She was using a D7000 and I am using the D5100.  She upgraded the D7000 to a D600 and sold the D7000.  I could have used the D7000 but I actually like the metering and AF better on my D5100.  I don't know why I just get better results.  Maybe I have a really good D5100 and a crappy 7000.  Our selection of lenses is the 35 1.8DX, 50 1.8FX, 85 1.8FX.  And the 55-200DX zoom.  All Nikons.

I keep going back and fourth on upgrading the D5100.  I think I will stick with it a while since i'm only the 2nd shooter.  My main job in the weddings is to try to get a few candids, take some detail shows of the venue, cake.  Also if it's outdoors to get some close up shots at the ceremony, and some expressions.  I don't use the zoom indoors it's just not fast enough.  Unless things are really lit up.  What do you guys think?