Thanks to all for your responses. If I do go the trust route, the trustee will be a financial services company, not my healthy son.
And yes, I will consult my estate attorney for his suggestions on language, but I want to do my own research so I have a menu of options. The problem with relying blindly on an attorney is that you don't have any yardstick to measure whether your attorney has done a good job. If s/he hasn't, it won't be apparent til too late to do anything about it.
Here's an article I found that advocates very detailed provisions for distributions to beneficiaries with addictions (see pp. 18-20).
http://www.aureusinc.com/pdf/Demise_...iscrestion.pdf