As my mother's POA, I'll be signing for the sale of some jointly owned property. What does my step-dad have to sign papers for this?

This property is farm land left to my mother, her brother and her sister by their mom. I'm the trustee of that property and according to the will, the inheritor of my mother's part of the remaining farm land. My step-dad signed a legal document several years ago stating that he has no interest in the property that she inherited from her mother. The lawyer said that technically, my step-dad does not have to sign, but since he signed other paperwork in the past related to the sale of lumber, etc., we should follow that example. My step-dad's signature will also require a noteray which proposes the challenge of getting him out of the house and into a bank in a wheel chair and keep him awake long enough to understand what he is doing and sign the thing. That is sad. He still signs his tax returns once the CPA has completed their preparation, but otherwise his son takes care of the payment of bills and my step-dad's trailer park.