Well there are plenty of options atleast
First of all, option set one "Do i want to keep the elderly in the active family, yes? no?"
If not, moving them out as they get to live the rest of their lives as they wish, without control from "the watchers" hands, which itself doesnt sound that bad type of "retirement" - Being truly free

Option set two : If yes, where to keep them, which can be everything from garden shed or mini mansion in the backgarden, or top floor of your house. Or like me, build large suite with great beds, good kitchen, TV and skill items.
Or you can choose to just kill them off, as they basically served their purpose( and no, i dont use this one myself, as i, like other sim loving players, gets
really attached to them.)
But i usually also use having two suites, one for the elder couple, and one for the heir couple, and the the having single beds, and finally the woohoo room
