Actually, we're having two receptions.

After our ceremony we're having a short (3 hours or so) cocktails and hors d'oeurves reception for family and close friends. (about 125 people)

The next day we're having a gigantic, more casual reception where we've invited everyone, their brothers, and their dogs (okay, maybe not!). Everyone who was at the actual ceremony is invited to both (the cocktail reception was mentioned at the bottom of the invite, and the casual reception was listed on a reception card). That one will probably be closer to 300-350.

Seperate, less formal invites are going out to those who are invited to the larger reception only.