I have found that the Parkinson’s Disease Foundation is the best source of up to date multi-method delivery of information. See http://www.pdf.org/en/exercise.
One of the presenters of a teleconference session I attended through PDF was both a physical therapist and a Pilates instructor. They seem to support various modalities. I believe PDF provides an exellent newsletter, blog and education reading.
Bottom line- keep our clients moving and keep them strong. 50% of a PD clients functionality is about exercise and 50% meds. I work with my PD clients minimally 2x’s a week, to 4x’s, depending on their ability to work on their own, for one hour. We do strength exercises, fear of falling drills, rapid execution drill, freeze drills, practice speech, and stretch.
I commend your efforts and that of your client. It is a rewarding niche.
If you have any further need for assistance, you may contact me directly. See my IDEA profile.