I laughed when I heard your question about crumbs in their pockets. I remember being concerned about the food still on their faces!

The bears in Yosemite are most likely to hammer a minivan, because they know it will have food, somewhere, in it!

Be cautious, teach them well. They have a lifetime to figure this stuff out (or at least ten years) so don't push too hard. We were much more cautious with our kids when they were little. You don't to terrorize them, but you also want them to understand that sneaking a graham cracker into the sleeping bag is a really bad idea.