What about a night at a hotel that has a pool and gameroom? The first thing that came to mind was Kalahari near Cedar Point. I've never been there but know that my friends have had a great time there. This would be more than $150 but maybe another family member would want to go in on it, too. If you didn't want to do such a big waterpark type place, maybe you could find a hotel that would have winter specials. There are some around here that will do movie and pizza nights with a night's stay.
My other idea would be gift cards to a movie theater. Our kids love to go to the movies and indulge in the popcorn and candy, but that is such an expensive treat. If they had gift cards, they could enjoy the movie without thinking about how much they spent on it.
Good luck! I'm anxious to see the other suggestions. I'm always looking for alternatives to just giving more 'stuff'.