For a serious student, I assume you and your child are serious because you are reading this blog, at least twice a month. To achieve best result, try one tournament every week. Pick any outstanding chess player, and looking at their forming ages, you can see the same pattern about tournament number. The stats strongly convinces me that how many tournaments you play determines how far you can develop your chess career.
Check out the following examples, you will see the pattern by yourself.
Hikaru Nakamura: http://www.uschess.org/msa/MbrDtlTnmtHst.php?12641216.10
Park Zhao: http://www.uschess.org/msa/MbrDtlTnmtHst.php?12787319.9
Sarah Chiang: http://www.uschess.org/msa/MbrDtlTnmtHst.php?13091081.16
Carissa Yip: http://www.uschess.org/msa/MbrDtlTnmtHst.php?14514636.4
This is also the reason why there are more good chess players around those chess centers: such as NY/NJ, CA, and TX. If you check the nationals or top 100 lists on USCF, most top players are coming from these states.