I think he is leaving his in-laws dinner party and going to a hotel.
Why do you think he wants to stay in a hotel?
So he can spend time alone with his girlfriend.
While it is good to want to spend time in a hotel and enjoy being taken care of, you should not abandon your in-laws. They will be angry and upset with you.
They have their own lives to live and sometimes we need to keep privacy.
I think that if there were a lot of tension it would be OK to stay at a hotel instead. Otherwise, while visiting your in-laws you should make an effort to spend some time with them and not fly the coop.