Sex at granpa's

My partner and I always have sex at my place, even when my parents are at home, which is only sometimes. Today I didn't want to cope with that feeling for I knew my grandparents have gone away. So he and I are going to go there to be intimate. It's the first time I do such a thing and I feel bad.

Btw, I have the keys but they don't know I'm going there, obviously.

Is it wrong?