Translation:Tomorrow we are going to my sister's house.
I would say it's a bit more than awkward; I doubt it's something many native speakers would say. To put it in perspective, "my sister's house" gets 150 hits in Google, "the house of my sister", 22, and those are mainly in grammar discussions about how English possessives work. The handful of examples in Google Books are mainly from the 19th century:
Five years ago it was pointed out the "head to my sister's house" is an idiom, and that a perfectly acceptable translation is "to go to my sister's house".
Five years later, it's not fixed.
Why do we post bug reports, if not in the hope that future learners will benefit?
You're right. It's not incorrect. It does, however, sound a bit strange. Normally I would say "My sister's house/home" and not "The house/home of my sister".
Perhaps other English speakers would say "the house of my sister".. I don't know. But in my opinion it sounds weird, although correct.