I think it is a good idea, but I would be less strict about the "time frame".
I think amends are best when the addict is in control of them. You might discuss with the addict if he even PLANNED on making amends, or if telling you and apologizing is what HE thought was enough.
Most addicts don't get to the amends stuff until quite a ways into program.... mainly, because for the amends to be meaningful, they have to do a lot of footwork first.
Does your husband just want the money? Or does he want it paid back with money the kid earns (and values) and after you son is in a place where the hurt of the theft can also be addressed?
Perhaps explaining that an amends is expected "at some time".... would work?
Just some thoughts...