I think "scam" is a little strong, because this is basically standard practise as far as I can work out. Ticket prices are nominal, but the ammo can really cost a lot. However, while this is fine for a bunch of 30-year-olds on a stag weekend, it is completely unsuitable for a children's party. The kids will obviously blast away indiscriminately, then cry when they run out, leaving the poor parent with a bill for hundreds of pounds. They should offer fixed priced packages, with a set amount of ammo which is allocated before each game.