I love LivingSocial (daily deal site) as there are plenty of discounted deals focused on family orientated fun.
In the past I've purchased a horse riding camp for the kids, free and cheap movie tickets, magazine deals and even a family weekend away to the Poconos...
There are deals for many US cities and suburbs that enable you to entertain your family at an awesome price. The deals seem endless.
I have my eye on a MyGym Deal (Philadelphia North) Four Gym Classes, Four Free Plays, and Lifetime Membership for only $49 (typically $149) WOW
Go check it out here
Oh and right now Living Social is offering a free $10 credit to the first 20,000