LD, I would definitely pump in a quiet room at the BBQ. It'll be welcomed and probably open up some great conversation as people are always curious about inducing lactation. Great job on the progress you're making with milk production!
Sandra (wife to awesome DH Jeff, mom to bio DS Tony 17yr., adopted DS Nathan 6yr., and adopted DD Jaida 14mos. and still nursing-was on accelerated protocol for 70 days)