I'd set a small monthly spending limit for the fun stuff ($50 month) and buy prepaid credit cards for each month. tuck away the higher credit limit credit card in a place that is very hard to access.) Then use the prepaid cards - one each month.
http://www.creditscorequick.com/blog/2010/08/29/5-tips-to-the-perfect-prepaid-credit-card/ (I am nor endorsing any the site - there are many places so shop around)

You can also get a prepaid debit card
http://www.bankrate.com/finance/credit-cards/don-t-overpay-for-prepaid-debit-cards-1.aspx