My daughter has stayed at the Harbor Club (Boardwalk), Mouseketeer Club (Grand Floridian), Sandcastle (Yacht Club/Beach Club), and Neverland Club (Polynesian).
Her favorite is the Sandcastle. However, many posters on this board give high marks for the Neverland Club (my daughter though it was just 'okay.' I think she felt this way because there were no children her age (at the time 8) at the Neverland Club. She generally finds a greater number of children her age at the Sandcastle Club.
In the clubs, there are plenty of activities for the children (games, arts and crafts, etc.) You also have the option of letting your child have dinner.
Some of the clubs have a four-hour stay maximum. I don't think Neverland Club does, but should verify that with WDW reservationists.