Dinner Group
My husband works at a very small private school (15 teachers total K-8). Our friends (who teach at the school and their families) have a "Dinner group" that runs during the school year. My husband and I joined it when we moved here. There are 7 families in the group and each month we make up a calendar for who will make dinner for weeknights (M-R on days school is in session). Each family signs up for 1-2 nights a month to cook dinner for everyone.
It was sort of overwhelming at first because if everyone comes there are around 25 people, counting kids. But, it's great because I only actually cook dinner 2 weeknights a month! Other nights someone else cooks! And it is very casual so if something is going on, you aren't required to be there. (Some people are taking grad. school classes, others miss nights for school sports events, etc.) And, if there are big things going on at the school (programs, conferences, etc.) we just don't have dinner group that night. Plus, no one gets mad if you are supposed to host but have to cancel.
I really like it because it's nice to sit around for a little while and chat with friends after a hard day with kids. The kids get to hang out together and are practically a family. We usually have dinner from 6pm-7pm, and it doesn't usually go more than an hour because since it's a nightly event, people don't feel obligated to sit around forever and talk.
It's not something that would work for everyone, but if you have some close friends at your school or in your neighborhood or whatever, I highly recommend it!
PS- Cooking for that many people isn't even actually that hard either. People tend to rotate through a few of their favorite recipes. I usually make baked pasta, homemade chili, or something in a crock pot - and then salad, bread, and cooked veggies. Some people will just go to Little Ceasars and pick up pizza!