If I want to incorporate a non-profit booster club for a semi professional baseball team do I use 501 (c) (3) or 501(c)(7)

Not 501(c)(3) - your booster club does not meet any of the categories of organizations that qualify as a 501(c)(3) - see pub 557 for information on what types of organizations qualify:

Publication 557 (3/2005), Tax-Exempt Status for Your Organization (http://www.irs.gov/publications/p557/ch03.html#d0e4545)

Your organization is more like a social club, and therefore 501(c)(7):
Social Clubs (http://www.irs.gov/charities/nonprofits/article/0,,id=96189,00.html)