My boys are older (30 and 33) but my wife works in a school so I have been tied to a school schedule since my first timeshare resale purchase in 1996 (they were 5 and 8). Summer, winter/spring breaks and Christmas tend to be peak travel for air fare and high demand for trading/ exchanging. We are a beach family and and continue this even today when schedules permit and we travels as a family. Over the years we traveled outside of timeshares so a bridge between the two worlds were important to us. One last point, between the junior year in HS until college graduation, my wife and I became the boring dopey parents that were too boring to travel. Translation, it was too much fun being home with friends when we went away. It is amazing how smart and how much fun we became after they started funding their own vacations when done so outside the family travel. I hope it doesn't happen but if it does, you are not that far away.
Starting point, you can see yourself going to one location every few years., you enjoy beach and you are tied to peak. You need to buy premium resale week. If that location you can see yourself going to every few years is Hilton Head, I would suggest the Grande Ocean. Great location (near Sea Pines with access to Sea Pines), on the beach and great pools. It trades well into other high demand locations. You can get it at a reasonable cost. I just purchased one for $9,400. The maintenance fee is not too bad (abut 1600).
You are going to need maximum flexibility because of your peak travel requirement. Some people believe points do that and I won't disagree but cash does it better. The Grande Ocean can be rented for between 2700 and 3000. You can avoid trading all together and use the cash to rent where you wan to go. You can also use the cash to travel outside of timeshare. This was my bridge between the two worlds. If it is another beach location that you want to go to instead of Hilton Head, great. Just find one that rents well, trades well, and a reasonable cost and MF. Aruba, St Kitts and Frenchman Cove have high MFs and they are easy trades when it is not the winter.
I also purchased a pure trader in 1995 and still have one today. While the actually resort I owned has changed,, the way I use it hasn't. A trader is a resort that I will never go to, I got at a inexpensive price, has a reasonable MF and is a platinum week that trades well. 95% of the time I trade, I trade into Marriott's only. The trader I have is a Grande Chateau but there are other good traders that people can recommend. So since you have are an experienced timeshare owner, you can minimize your investment and go this route. I have traded my Grand Chateau for Aruba during the summer, Frenchman Cove April, Grande Ocean summer, Oceanwatch during Easter to name a few. I just picked up a Grand Chateau 3 bedroom for 3500. You can trade it as a 3 bedroom or get two trades, one as a 2 bedroom and one as a 1 bedroom.
I think you have a lot of options but do nothing until you learn Marriott and doing what you are doing. Read and ask questions. Good luck.