Does your son intend to be in possession of the item without you being present? If the individual reviewing your trust speculates that they may indeed do so, it could impact your approval.
Personally, I would never name someone whom is under twenty one, much less under the age of majority, as a trustee.
By naming him a trustee, he will essentially be able to have unsupervised access to items that he would otherwise be unable to acquire.
I'm not saying it would not be approved. I am just stating that you will have one hell of a court case on your hands if he was using the device unsupervised.
I am in no way shape or form accusing you of intentionally skirting the law. Nor am I attempting to undermine your intelligence. I just prefer my fellow enthusiast to think of the possibilities.