Re: a chore where/in which
Overlooking for a moment the fact that I don't like "while you are doing it" at the end at all, I prefer #2 of your 3. However, I would simply split the sentence:
Originally Posted by navi tasan
"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.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.