As the Mother of another Webelos Scout with ADHD, let me offer a differing opinion. I was my son's Den Leader for 2 years and he drove me crazy at every meeting. Other kids would have some of the same behavours (den of 14 - 4 with adhd) and I could ignore them, but when it was my son, i went nuts.
Do the parents hold positions in your troop? If not, perhaps it would be better for him if the parents didn't hang around the troop/patrol meetings. I only say this because I have moved from Den Leader to Assistant Cubmaster and my son is doing better in his Den Meetings without me around! Ba