Best wishes on a great decision. It's wonderful for you and the wife to get out there again and get active. We've all taken that first step here on this "Clyde" forum.
It's even more important that you ride along with your son, build your family time together and help him choose an active path to fitness. At this age he still thinks you 2 hung the moon and stars. Enjoy it while you can and be thankful he wants you along.