I'm afraid I can't answer your questions specifically, but we were there 2 weeks ago & my 5 yo dd went twice. She loved being a "L'il Rocker!" She said she was going "clubbing." The staff was very responsive--she was nervous the first night and one of the staff sat at a computer, put her on her lap, and played a computer game with her. You pay 7 bucks or so per hour, then I believe an extra 10 if they want dinner. So it ain't cheap. It was a godsend for us. Since they have playstations & nintendo, as well as a big screen TV, my 13yo DS was halfway tempted to stay himself.
I think the restriction for age was they had to be potty-trained. You could confirm it by calling the HRH & asking for the Lil Rockers club. I had made prearrangements before we got there.