Sitting may be extended for one to two hours in a regular chair with arms, but they still need to be doing something to prevent slumping and sliding out of their chair. The preferred method for sustaining their attention is apt to be hand-over-hand assistance to apply tactile cues to different parts of their hands and face.
Upper Extremity Range of Motion Exercises
ROM exercises can be done as described for ACL 2.0, with knee supports.