I usually have an heir live with or move back in with the parents. The elders help with the grandkids and are usually included in a lot of activities. I try to send them out to dinners with their other children as well or have group events for them. Recently an elder sim died during a family reunion for her when I'd had the old age death notice for her. It was kind of like all of her family gathered around her to say goodbye.
I have such a large rotation that there can be exceptions. I don't have a lot of elders living completely alone. Someone lives with them and inherits the house. I've used cheats like motherlode and I've sent inheritances with young adults who move out. If they add wills, I'd obviously use those. The non-heirs for the house usually get some simoleons.
