"A boring family gathering is like a chore - you just have to look happy while you're there."
I have a couple of problems with your suggestions. We wouldn't normally associate a chore with "where", "at which" or "in which". They go OK with "family gathering" but the construction of your sentence puts them closer to "chore". In the same vein, "while you are doing it" goes with "chore" but it doesn't go with "family gathering". I think you have just tried to connect too many different factors.