Since you have helped the family with their IEP you must know the mom well - if not friends but well enough to get a feel for her and understand how much she 'gets' her child. do you doubt her judgement?
i think a 16 year old can totally do it. they may not like it, but they can do it - even with all his other issues. perhaps he talks and texts his brother every day so he has some contact. even with depression and anxiety - this can be a very empowering moment for him. esp. with IEP even more. gives him a chance to figure out that he CAN do it