In EY, we split it up, making a seudas chaverim for the Rebbe/Menahel and boys in the class – usually done at home, but maybe in a small hall if the family is very wealthy. This would be a full meal – on hamotzi. This is usually done on the day of the Bar Mitzvah itself.
For friends, both of the family and of the boy who are not in his class, we make a kabbolas orchim, where mezonos, salads, desserts are served. Most of this can be homemade. It’s like an open house where people come and go. Many people I know make it in the house and others make it in a small hall. Only very wealthy people have made it in a larger hall. I made this for my son the night of his Bar mitzvah, but it depends on when this happens (what if it is on Shabbos/Yom Tov). I also know people who just make a big kiddush (like for an aufruf) the Shabbos of the leining. This can be done in the house or at the shul’s hall.
For family, people can make a special meal for the whole family, making it as extended as they like. Many people make this right before the kabbolas orchim at the same hall.