I haven't had the opportunity to sing in the mountains, yet, but I have been lucky to have a few wonderful outdoor experiences. My father is a buckskinner and he hosts an annual rendezvous on Labor Day in New Limerick, Maine. (Check your maps!) One year it was cold so we all crowded into one of the teepees. There were 25 of us in there, singing and talking while the night got colder and colder. Finally I went out to get a breath of air and check that the stars were still there. The northern half of the sky was painted with the most breathtaking wash of color as the Northern Lights flared and danced.Then, more recently, I was hired by the Maine Schooner Association to provide entertainment for the schooners gathered in North Haven inlet for the annual race. They floated us from schooner to schooner on a scow sloop. We had a harp, fiddle, guitar and five voices. That night we sang on board one of the schooners and then slept on board. I woke in the early dawn and went on deck. There was a heavy fog which lifted as I drank my coffee. The sight of the thirty or so schooners slowly emerging from the fog is one of the most memorable sights lodged in my mind.
Joe, I don't think there is anything you can do about the sound outdoors except try to situate the singers with their backs against a wall or other hard surface. That's what we do when Roll & Go is singing in the streets. It bounces the sound out to the people. If you are going to be around the campfire I guess all you can do is make it a small fire or just settle for what you get. If you make it a small fire people may sit in closer. Good Luck and have fun.