Working with someone is a very delicate situation, as you probably know. Before doing anything, I would do some PNF patterns and trunk stabilization exercises with that person first. Only after that, would I do balance exercises such as:
Sitting Balance on SB (1leg on floor)
Do the same exercise; except this time, the client has his/her eyes close.
As the person gets better, then the balance execise should get a little more proactive, such have the person sit on the SB and apply a gentle pressure to the client to provoke balance.
Best of luck