ALthough not from experience of my own (I have a 8, 7 and 5 year old) as we have only been on Disney and Carnival, I have done a lot of research on the web looking at reviews, write ups and other information. From what I can tell, it seems that the Voyerger class ships on RCCL are clearly worth a few extra bucks as they are bigger and have more to do.
From the post, I can not tell if you are in Florida or not but you may be able to find a very affordable rate on a seven day cruise from Miami on one of the voyerger class ships. From what I can tell, Saturday departures are cheaper than Sunday and it is even easier to find at non peak times.
Right now, we are deciding between Princess and RCCL...but I think it is going to be RCCL Explorer for us.....
I have had the same issuse to deal with. I have found so far by far Rccl is worth the few extra bucks. And I am going with teh Navagator. I used the Bargin finder on this site and got a cabin for all for of us for a 7 day cruise for $1900 WOW waht a savings. Try it. You will save $$$$$