But when it's a light kid crowd, they will combine the 6-8 and the 9-11a together. So your 5 year old will be in with kids about to turn 12.
And in those clubs it's not a "wander and do what you want" place where you can sit and color or play codes games all day. It's a game-playing, group activity place.
I don't want a 5 year old playing gagaball (which is as close to dodgeball as it gets these day) with my kid who was 11 last cruise and already taller than me. It's not fun or safe for either. (DS has to tone down his fun, your kid is dealing with more physically adept people, my son is in danger from falling from his height (and a recent fall caused him to break his arm so I don't want a repeat) and your kid might be who he trips over. Neither side is good to be on. I've been on both sides as a parent and DS has been on both sides as a kid. Not fun. )