Actually.....from a chemical standpoint the chocolate breaks down the calcium and your kids get less of it when you add chocolate. I did some homework on the subject when the chocolate calcium "candies" came out on the market.
You're probably better off offering your kids a homemade peanut butter or oatmeal cookie with that glass of milk.
I can dig up some of my links if you'd like, just let me know! : )
Nancy BellaOnline Yoga Editor