Even though my son is a lot older than yours, I would never think of saddling him with DVC member fees. He gets to enjoy the points with us. But he hasn't gotten a chance to enjoy them without us yet. Not sure that is going to happen. Ever.
When we bought in 1997 our OKW dues were just over $3. Now we pay about $5.50. And for the first five or so years, they stayed fairly constant. A few pennies up or down (the last time they went down). They will continue to go up exponentially in the future. Unless you also leave a pretty nice inheritance to your kids, don't plan on passing them on.