Before you say the gum leaving is all about your DS, consider this:

Would you still want change without your DS about? (I would, who wants dirty used gum around anyway? I wouldn't even mention DS as it isn't acceptable without a small child around either.)
How do the boys feel about DS? Do they visit to see him (so good, behaviour needs to change because of DS) or do they not really care about DS (we were here first/don't see surprised as much cos of DS - so don't blame him for this!)