Couple of practical things to think about as well, one is a personal alarm that would alert you and some others (neighbours for example) if he had a fall. I know in my area there is a local voluntary group that sets these up through I think Eir.
Secondly is there anything like an elderly group he could get involved in or visit. In my area, my Mam gets picked up on a Tuesday morning by taxi, taken to the day care centre where she gets mass, dinner, meets other people, a hairdresser comes in, lots of things going on and she gets dropped back to her door by 4, all for €15.
Also consider meals on wheels.
Speaking from experience with my own mam as me and my family live a long way away, a lot of this is almost like have people checking her daily without it seeming like a check.