Keep an eye on DS5. Some of the triple digit math doesn't get introduced until 2nd grade. I think its great to nurture his passion with math games. We did that with DD, now 5, by using her favorite things. For example, if she had 7 cupcakes and she gave 1 to Dad to eat and 1 to Mom to eat, how many are left wtih her? Just weaving in something interesting can keep them hooked... Happy Holidays!