We did it in May for my sons 11th birthday and he loved it. There is a discount. I believe it ended up being around $25 give or take a little. The instructors first went through and taught the kids the rules and safety. They start very close to the targets and then they scoot back, shooting from 3 different lines. They do take things slowly because there are people of different ages and experiences. I'm not sure how advanced your niece is with her bow, to know if it would be boring for her or not. For the price though it would be fun for her to try. Like I said my son loved it. He too has a bow, but not a lot of experience with it.
Note that the location in Ft Wilderness is where the bicycles are rented and near the main pool. We were told it was near the dock/ stables. By the time the internal bus driver stopped talking to another bus driver (for 10 minutes after I started timing it) We were close to being late and had to walk very quickly. Had I known we needed to take the internal bus I would have given us more time.