Here is what we do as a family and so far, it has worked for us. At the beginning of the season, our boys are weighed and automatically put in a weight-bracket ABOVE what they weigh. That way, they don't have to worry about making weight, even during Christmas. When it comes to sub-district, we see where they are and put them in their "natural" weight-class. In the past two years, both of our younger sons dropped a weight-class because that is actually what they weighed. Then, they only have to deal with maintaining their weight for three weeks at the most. I have never had them lose weight for kids wrestling and unless your son/daughter is overweight, would strongly advise anyone against it.
Now, there was a year in high school where our oldest son had to drop 15# to wrestle. This was because the team needed someone at that weight. When he came home and told me, I agreed but ONLY if he followed my rules and we did it healthy. I made up a diet for him to follow full of fruits/vegetables and lean protein (plus eating 6 small meals instead of 3 big). He also increased his running from two miles a day to four miles. It worked for us and kept him healthy. Looking back, I wouldn't have even considered doing it if it wasn't because HE wanted to and he was old enough to decide for himself.