My 12 year old did it twice earlier this month on Fantasy. He had an awesome time. (We reserved one 30 minutes session and then managed to book another onboard after he enjoyed the first one.)
You have a whole selection of different games to play (baseball, basketball, football, hockey, "carnival games", cricket, etc.) For example, on the football you can do a 2 minute drill passing game, you can kick field goals, etc. One side just has the games, the other side has the games as well as golf.
The fee is for the time slot, and it does not matter how many people are playing (even though I only saw one and two player games, so people would have to take turns). So the 2nd time around, although I had only signed up my son, he played solo a few things and then we also played a few things together.
Grab the 60 minute slot; you'll love it.