I actually attended a "covenant ceremony" last week that fits your description. A local rabbi and her husband chose to have the bris done by a mohel, with just their immediate family in attendance. The rest of the community of friends, extended family, members of her congregation, etc., were then invited to join the "ceremony," which included the announcement on the baby's new names (English and Hebrew), explanations of where the names came from, some rituals symbolizing the baby's entry into the community, and then the celebratory meal (a light breakfast).
They included in the program they created for this ceremony,
What about the circumcision?
With the blessing of warm community, we sought to welcome our child into the covenant with both intimate and public dimensions. We are also dedicated to celebrating our child's arrival in a way that doesn't over-emphasize a baby's apparent sex. We developed this communal ritual for any child. As our child is a boy, we held a private circumcision ritual for only parents, grandparents, uncles and aunts. Had our baby been a girl, the private ritual would have been immersion in a mikvah.
I hope this is helpful as you plan your son's circumcision and celebration.
