To save yourself the hassle of a bbq at a later date, why not organise a 'wetting the baby's head' get together at a local pub/cafe. We did this for DS, when he was about 4 weeks old, and it started off with arvo drinks, and then a good sized group stayed on for dinner, it was totally chilled, and it meant there was no shopping or cleaning or preparation, everyone bought their own drinks and food, and we got to leave when we'd had enough.