We were on the Liberty in February 2006. There were about 250 children out of 3,000 passengers. An employee with the children's program said they typically have 250-300 children per sailing during the winter months. However, she said they get as many as 800 children per week during the summer.
Although we did not have our children with us, all of the children we saw seemed to be having a great time.
Hope this helps.