Activities/restaurants that can accommodate a group of 15 people in Tokyo?

Heads to Japan with a fairly large group, we’re from all over the globe and are in our 30s.

I want to ensure we are respectful of facility capacities, and we are currently planning the trip for Mid-late November.

We are thinking an onsen day trip as one of the activities, but I’m interested in advice and suggestions for more activities and food spots.