How many computers are in your environment and do you have Remote Desktop? If you have ARD, just select all the computers and run the command gracoat posted. Again, though, just make sure the path and everything is accurate. Conversely, if you have a relatively small number of computers (I'd say 30-40 would be about the max sanity limit), just go through them manually (could probably put a script on a flash drive to speed things up a bit). Now, a lot of computers and no ARD, you may be stuck with the two options you listed.
Although, after typing all of that... If you have it remove the home folder on logout, even if he logged into an old one and synced back to the server from it, wouldn't it just delete it off that computer when he logged out? Sure, it would be back in his account, but it wouldn't continue to be spread around to other computers and would essentially self-sanitize itself from any computer he visits. Of course, depending on exactly what the content is and your policy regarding it, you may have to deal with his account again, but it would just be in the single location of his mobile account.