One of the favorites was chocolate chip cookies. One granddaughter from each mother loves to cook, and had been "cooking with grandmother" since age 4, so there was quite a lot of merriment in the kitchen, which the boys were either banished from for bad conduct, or were living in a self-imposed exile until it came time to partake of the fruits of the girls' labor.
Soon, Grandfather caught the boys on the ROOF! In the course of the debriefing involved with this senseless and dangerously deviant distraction, the boys claimed to be conducting surveillance.
They'd peer into the kitchen to see when the coast was clear, slip in, and pinch raw chocolate chip cookie dough, then climb back up on the roof to eat it.