Your son will thank you.
My son inherited the mountain bike that my DH rode from 1998-2000. Then it got converted for me to ride on the road, with slicks, etc for a couple of years. From 2002 until 2006 it just sat around in the bike shed, getting occasional use from a guest. We pimped it out a bit with a rack, pannier, light, etc. and I used it again as an errand bike for 2 years. In 2008, we gave it to our son. Last summer, realizing he was not in good shape, he began riding it on the bike path and to work. By the fall, he was riding with us. Then, he got a hand me down from his younger brother, a classic steel Serotta road bike. We thought the double might be tough for him, but no, he now out rides DH. And he bought himself a single speed to commute on, but he still rides that yellow mountain bike at times. It's been in our family for 12 years and i have a real sentimental attachment to it.
2015 Trek Silque SSL
Specialized Oura
2011 Guru Praemio
Specialized Oura
2017 Specialized Ariel Sport