Hi Alex,
That's a hard question. The Doc knows the usual time-frame for healing, and expects that one will have to push the envelope a bit to recover. The therapist sees your Dad more often than the Doc, and therefore knows Dad's current issues. So, notice the little things, i.e. is he swallowing his own saliva? Can he let a small ice chip or a popscicle melt on his tongue and swallow it without choking? The issue is aspiration pneumonia from breathing in what you should be swallowing. At any rate, I would have the therapist there the first time I tried it, just in case.