Another thought--is there a local sports team that they might like? My DH is a huge baseball fan, but major league tickets are out of the question. But there is a local summer college league, where the tickets are less than $5. It's a very casual atmosphere, they give out prizes and have music, a snack bar, fireworks, and so forth. Back at our last home, the field was a mile from our house--I would drop off Dh and whatever kids wanted to go, and then they would walk home afterwards. My kids would run into friends at the games, and generally have a good time. Something like this might be fun for relatively low cost.
As an aside, our local baseball team gave out some wacky prizes. Our family's all-time favorite was winning the "couch potato family". They got to sit on a couch behind the catcher, and were brought all the hotdogs, popcorn, and soda they could consume for the entire game. I think they also got their name on the fancy scoreboard. Occasionally, players would come over and sit down for a minute or two. And you know, for the team, this wasn't really an expensive prize to award, but it made my kids fans for life.