Welcome to the club!
I bought my first bike about 4 years ago when I was ~46 and my kids were 15 & 17. The primary reason for buying the bike was that my wife's parents and brother lived out in the desert and we would go visit a lot. Her brother rode and he would occasionally invite my son out to go ride the quad around in an area not far from home. I bought the bike so I wouldn't get left out (or more precisely, left back at the house to be talked at endlessly by her dad....)
Then my wife started feeling left out, so I bought her a quad. Then my daughter felt left out so I bought her a quad. Then my son bought himself a bike.
Now days, instead of traveling to the deset to visit the inlaws and get a little dirt biking in we travel to the desert to ride and get a little visiting in! The entire family will enjoy a mild ride, my daughter and I can tear it up pretty good, but man, when my son and I go tearing off...... Let's just say I usually come back a little worse for the wear (sometimes a lot worse....)
Enjoy your sport and the bonding with your son.
Rod