I think I can say I've been on most of the mainstream lines heading to Mexican Riviera (except Celebrity, oddly enough).
At any rate, if you are bringing kids, you can't beat the Carnival Pride for its activities for them (and a wonderful ship, to boot). The balcony cabins are very comfortable.
RCCL's Vision provides a smaller ship feel with lots of glass everywhere.
Princess' new Sapphire (sister to Diamond) has got to be one of my favorites. Love the personal choice dining with 4 theme restaurants to pick from.
All of the above sail to Cabo, Puerto Vallarta and Mazatlan.
Your other option is to take the 8-night cruises down to Acapulco, Ixtapa/Zijuatenejo, etc. which offer wonderful ports. Carnival Spirit and NCL Star do those. I think there may be an odd Celebrity trip down there, too.
Anyway, that's some thoughts.
__________________ Harry Martin
Moderator - Mexico and G/L message boards