Based on our experience the last two years, the 3-4's stay in the Oceaneer's Club for all of their programming. The 5-7 age group has activities in the Club as well as the Lab, so they get to experience alittle of both. The 8-9's and the 10-12's are exclusively in the Lab. Personally, I would put your daughter in the 8-9 group if she is turning 8 on the cruise. There is a big difference in 5 year olds and 8 year olds, and she would probably enjoy the activities aimed more for the older group. It really just depends on the child though. Our last cruise, my son was within 2 months of his 5th birthday and the counselors offered to move him up to the 5-7, but my son wanted to stay in the 3-4 group and stay in the Club! It worked out well for us, our tablemates had a 4 year old ds also and he and our son became friends and enjoyed going to the Club together. We are cruising again this November and our son will be 6 years old by then, so will definitely go in the 5-7 age group this time.
Have a great cruise!