When I joined the Troop 3 years ago the standard was (and still is) Mr./Mrs. from Scouts to adults and adult to adult in front of the Scouts. I picked up on how much better the boys behaved, and still being active in the Pack, took to calling all of the Pack Leaders Mr./Mrs. in front of the boys. Without requiring it, all of the other adults caught on and it has had a positive impact on discipline in the Pack. I believe most of the Cub Scouts were using Mr. and Mrs., but the adults using formal addresses between each other had an extra, positive impact.