My wife earned her first degree in Music Therapy and worked in the field until we had kids and she stayed home.

It's hard to point you in any good direction - but know that music therapy is more therapy than music, and piano is an unlikely candidate.

The basic premise is to avoid the YAVIS principle. That is, that Young Affluent Verbal Intelligent Successful patients do very well with talk therapy, and the other 99% of them are hard to reach. So you branch out into music, dance, sports, occupational, etc., in an effort to connect.

Music therapist are not required to play at high skill levels. They deal hands on with very low functioning patients - in my wife's case with profoundly retarded, adults who functioned at a 3 year old level. People who are not continent and will never learn to dress themselves.

Piano isn't good because it interferes with you getting your hands on your client. Almost any other instrument isolates you less. Of course piano is a required course in the curriculum for other reasons but it is of little use in actual practise most of the time.

I do want to add that at this time I am working with two students who are described as "high-functioning autistic",

Perhaps other instruments would help even more, but both seem to make a connection with the piano and love the structure of the instrument.