I think it is quite good -- it can cover any number or prior commitments to your family. PLUS - it saves you feeling you have to explain your great-aunty's medical condition since sets it up as a formal event or a responsibility which you cannot wriggle out of. The other person would have to be quite pushy to ask you for more detail once you said this!Hi,
I wonder if I can call "the gathering with my family members" a "family engagement", as in:
-Are you available tonight?
-Sorry, I have a family engagement.
I guess I can, but maybe it's more formal than "gathering".
Thanks a lot