I started riding (real) motorcycles at age 52. Over three years I went from an Intruder 400 to a Honda shadow 750 and, for financial reasons, to a 250 Kymco scooter for an additional 2 years. When money returned

I bought a Rocket lll on which I could only tippytoe even after the dealer lowered the front. Short version of the story, the first day I rode it I took it out to the countryside with some friends; I was going to brake coming to a curve and I braked as in a scooter, which resulted in depressing the clutch, and when the bike didn't slow down I panicked, forgot everything I knew about riding, drove straight, the bike flipped lengthwise, I went over the handlebars, landed on my head and lost consciousness for about 15 minutes. My buddies helped me and I managed to ride it back home. Amazingly, NOTHING happened to the bike except a scratch on the pillion seat's sissy bar backrest (GO Triumph!!!).
All this to say: make sure to let him know to take it easy until his mind learns the difference between a scooter and a real bike's controls and he does it automatically, without the need to think.