I spent a couple of minutes looking all over google (that's about an hour of realtime) for hints or clues and came up empty. All threads lead to deadends or to commercial and for-profit rehab centers where bikes were shown on the grounds of the compound.
Here's the thing: Recovery is impossible to enforce without placing the recovering individual in a locked room. Because you may not have personal experience in a 12 step program, or a support program for the family and friends of recoverying addicts, the rest of the people on the trip must be emotionally prepared to detach with love and allow whatever happens to simply happen. Speaking from experience, those of us who want to--and feel they can--help, this is very difficult because we think we can control the individual. Your motives are worthy but it's not a trip I'd do without everyone receiving extensive training in, as you say, behavioral specialization.
There simply MUST be a therapy and recovery group that offers bicycling experiences. I hope you find one soon. Please consider coming back and telling about this adventure if you get to do it.