DS1 had a decent size party, I think about 40ppl & 10 kids. It was more of a celebration for us though really. We put a full lunch & drinks on and hired a local hall, as our house isn't big enough.
DS2 will be much more low key, it will only be my side of the family invited. ExDH's family never contacted after he left us (even though we had an ok r'ship) and haven't even made an effort to meet DS2. So they sure as sh!t won't be invited to his party.