Hi, Benny,
Having had a handicapped wife, may I offer a suggestion for you to consider?
Lay down a path of gravel, about 3~4" deep by 24~30" wide, well packed down, along that path by the rail, and leading to it. Your father-in-law does not need slippery ground under his feet and I see leaves which hold moisture. And how muddy does that area get after a rain, etc., etc.
Nice job!
