Of course it is ok to bring a DSLR or P&S, but not for PORTFOLIO building! It is just not right to put all of these photos on your portfolio like if you were the official photographer.
Ill give you one example. Lets say you were the official photographer. You did the wedding gig and there are several uncle bobs (very common). Now two days later you see several photos on facebook by one of the UB with signature on the bottom right (so and so photography). He/she did hideous processing (white vignette, selective color, fake tilt shift, etc. you name it). Would you care? Now everyone thinks those photos are the official photos? You wont get any inquiry from most of the guests because they think you are not very good.
I am not saying the OP's work is horrible. They are actually really good. I just dont like the action he took. There are a lot of photographers out there who rely on making money on prints. Doing this will just give your future business a bad name (if you are planning to do wedding photography).