Jasper may not formally be recognised as an assistance dog but that's what he is to my son. He got DS to go out, taking part in fun shows without me being in the ring with him, I can leave them at home (for short periods) as son feels safe at home if the dog(s) are there with him.
My understanding of assistance dogs, certainly those trained for help with autistic children, is not just to be able to get things or draw attention, but to enable a child to be able to live a little bit more independently.
Heidi is now also drawn to son (although it took a while as he can be a bit vocal which Heidi didn't like) and Charlie also seems to like to seek him out (and enjoys going into the special needs school).
Louie is less of a person dog so I'd be less likely to cast him in the role.