Threads are supported on Matrix as of a week or two ago. They're no longer in beta as far as I can tell. I don't know for sure how well alternative clients support them, but desktop and mobile versions of Element do threads just fine.
Alternatives (Fluffychat, for example) are usually a while behind Element because of manpower. For example, native polls are in Element but not in Fluffychat yet. So, if you want to risk the transition, best to recommend the official clients first.
That said, I don't know how well threads will actually work in a family context. I like them as a concept, but outside Google Chat (where every message in a room is a response to or the start of a thread) I haven't seen them get picked up naturally.
Alternatives (Fluffychat, for example) are usually a while behind Element because of manpower. For example, native polls are in Element but not in Fluffychat yet. So, if you want to risk the transition, best to recommend the official clients first.
That said, I don't know how well threads will actually work in a family context. I like them as a concept, but outside Google Chat (where every message in a room is a response to or the start of a thread) I haven't seen them get picked up naturally.