Check out Certifikid. A friend of mine (in real life, not one of my imaginary ones) just started working for this kid-geared Groupon/ Living Social type site. Currently their deals are not in Philadelphia but they are in Delaware, Pittsburgh, Baltimore and DC. I recommend signing up. You never know what great deal you will find to make a fun day trip for.
I will keep you up to date on the best deals I see. Try it out and let me know what you think. 🙂