This seems to be more of a local attraction than a tourist attraction. Ironically enough, that makes it perfect for touists -- rarely crowded and not overly expensive.
The Bucket Club (or Hartt Island, depending on whether you're talking to a local or the tourism bureau clerk) has mini golf, waterslides, and a driving range. They also have a huge are for RVs and a small campground. You can also rent kayaks and canoes and head out on the Saint John River.
Everything is very reasonably priced and you can usually get in full afternoon of mini golf and waterslides for around C$18 per person.