Good post. If I'm going to be "out" without my husband, I make a point of taking a child of reasoning age along. Not only is it edifying for the child to experience some adult life, such as a Swift-Vets presentation, but it sends a clear message that I'm not available.
My husband thought I was being overcautious, until he found himself in an uncomfortable situation with the single mother of one of the Cub Scouts in our pack. (Yes, she knew he was married with seven children.) He told me about it when they got home, and I just said, "Oops!" knowing that he can be naive, and then he said, "Next time I'll make sure I have some boys with me, if I have to go help one of the moms!"
In all the times that I've attended the Scout's Youth Protection Training, I always heard that we shouldn't be alone with a scout. It never occurred to me that I shouldn't be alone with another parent. Sheesh.