Do not spend the monies!!!! Unless there is nothing funnier (:-)
you can spend it for.
Like above post suggest, check out Aleks, check out Beestar, check out math games (like Descarte's Cove). There is hiennas(sp) around every corner trying to live of your insecurities.
Is there a math circle nearby your son could become a part of?
Can you organize one (I did), can you start an after school math club?