We just returned from the 5/3 Eastern cruise. My DD 10 and DS 7 had two different experiences. They both are also friendly and outgoing kids. My DD loved it! This was her favorite of the whole cruising experience, she happened to hook up via our cruise thread with another 10yo girl and the two e-mailed in the weeks prior so it was very easy already having a friend. She also loved the freedom of checking herself in and out and I was very proud of how she handled it, and followed all of our ground rules.
My DS just turned 7 but because he always wants to do what his sister does he was not as crazy about the Oceaneer club. He felt the 5-7 group were a bit young, he thought the Lab was much cooler and loved it when they brought the 5-7 goup in there. He enjoyed the specific activities, PJ party, learn to be a pirate, flubber etc. When I went to check on him in the pj party he even told me "thanks for bringing me on the cruise, Mom". But, every night they transition to "quiet time" where the whole group 3,4,5-7 are together and they lay on mats and watch movies, that is when he wanted out. It worked fine for us, because we had early dinner so it gave DH and I time for a walk or a drink after dinner and then we were all ready to turn in by 10:00 anyway.
Since my kids are the same ages as your I thought our experience might be helpful. I'm planning another trip in 2005, that way they will both be in the Lab it should work out great!