I realize that this reply is just a tad bit late.....like 2 years! Your original post said you would be cruising again with the kids in April 2008 and here it is April 2010!
But, in case other people are interested......I personally prefer Carnival. And......I don't have kids. I'm 57 (well.....almost 57) and I live in Houston so I've cruised out of Galveston many, many times. My favorite line in that port was the Grand Princess, which I sailed on 3 years in a row. But after she left, the choices were either Carnival Conquest or Voyager of the Seas. Having been on Carnival before, we decided to try RCI. After cruising on RCI, we gladly went back to Carnival. To me, the staff was happier and nicer on Carnival, the buffet food was better, and it was just more fun all the way around.