Hey Allen,
Hmmm, I see your problem; but I may also see a solution. Make him an offer he can't refuse.
If you've had any bright ideas already (and I bet you have

) outline them to him - in some ways, although he's your son, perhaps you should treat him just like any other potential client, and make a good, professional pitch.
You just need to talk - forget the phone thing, you give that boy a clout over the head from me... You need to reach an agreement to respect eachother's deficiencies - you don't get on his case for lacking motivation etc and he doesn't get on yours for lacking mobility etc. I know it'll take some talking, but it sounds like a very good idea for both you and your son. Sounds exciting, if I may say so!
Seems to me that you are both two sides of a coin - you've got the motivation, ideas, know-how and experience, he's got the brawn, muscle and (importantly) mobility. Plus, a viable business. So you complement eachother perfectly.
Find a good time to talk, somewhere relaxed and feel-good and talk around it first - stress his strong points, and yours too...then lead in from there. Most importantly, show him the wide extent of your experience and the wealth of your knowledge in the field - that's just sitting there waiting to be tapped. By him, if he so chooses.
I wish I could say hey, forget the RSD, just charge in there - but that is just plain daft. In the working world, a one-off is one thing, but the trick is to be able to continue, month after month, not overdoing it (if possible) so that you'll be OK for the next ones. You know this, of course.
I really hope he can see the light, it sounds like such a great plan.
Are you still off the ciggies? I kind of wish I could stop (it's banned all over HK now, so socially very unacceptable)...but ...well maybe some day!
Look after yourself, big guy, sending you loads of virtual hugs....your family sounds great, by the way!
all the best