another thought on tying those toes
If he/she is already wearing some kind of ankle cuff, or has something similar on to faciliate fastening to...
Then take your string, or shoelace, or whatever, and tie it around the big toe. Bring the other end down to the ankle cuff, through a rung in the cuff (or invent a loop with the rope), and bring back up to the little toe. Tie around that toe.
You will find that with only two toes tied back, the motion of the feet is severley limited. If only the big toes are tied, the rest of the foot can still sort of curl. But with the little toe also tied, those middle three can do nothin but go with the flow - they just cannot curl.
And presto, the foot is ready for your enjoyment.