No, balls can eat rats right out of the egg. Don't even waste your time with mice. You can pick up a cheap food scale at Wal-Mart or Amazon.com. Without a scale, just use your best judgement. Feed them rats that will be approximately as big around as the fattest part of their bodies. Most hatchlings have no problems with fuzzies as their first meals. Sight unseen, it sounds like you have the right idea with picking up a bag of fuzzies and a bag of pups. Worst comes to worst offer them two if they are on the small size.
200g at 6+ months? That is very small! With proper feeding they should be closer to 400-500+ grams at 6 months of age.