Parents are considering a dog, any advice or experiences?

My parents are in their early 80's, mother has early Parkinson's uses cane/walker, father with heart issues. They live in a retirement community of townhomes. They have a history of impulsive decisions. They do not react well to challenging dialog, even when it's very gentle. Over Easter they said they've been looking into getting a dog. While I understand that hole of not having a pet around when it's the norm in your house, I think this is an irresponsible decision. Neither can really get around great and I honestly think they are a few years away from assisted living. There was no talk about what the plan is if they can't take care of the dog in the future. Both my brother and I don't want another pet (and in my case, a dog would change our pet dynamic greatly as we have a free roam rabbit & 2 cats). Has anyone dealt with this? If this was any other sort of interest, like a plant or a car or a new house even, I would shrug it off even if I didn't agree, but this just seems different.