I'm with the don't-do-it crowd. If they were yours, it'd be different. But they belong to someone who wouldn't want you smoking weed anyway, much less out of something that belonged to her beloved mom. Can't you just get yourself a nice pipe of your own and smoke out of that? Raise a bowl in honor of both your mom and grandmom, since of course it is about to be Mother's Day, and congratulate yourself for not having stepped over those boundaries. Someday your mom will probably leave those pipes to you, and then you can do what you want. . .