Discussing work with supervisor in an invited dinner with his family
Welcome to academia.SE :-)

See, many things that we do in our life are most of the time unplanned and spontaneous. The thing that you did is not a big deal for good people. Just say sorry sometime during tea time and get on with it. Don't keep it scratching.

Further, one positive to that is: He would have felt so happy that he has got a very dedicated (and weird) student who shows results during family dinner.

I have done it quite few times and I am not sorry about it. It feels weird initially, but not so apologetic. 

Good luck!