OF ALL the things our kids enjoyed about our family’s annual weeklong summer vacations in Quebec City, their favorite was a small museum. Its official name was “Musée du Fort’’ — the museum of the fort — but we always called it “the diorama.’’ You sat in a darkened room looking down on a topographical model of 18th-century Quebec — houses, churches, trees and hills, frigates on the St. Lawrence River, regiments of tiny blue- and red-coated soldiers. A slide show on the back wall told the story of the long French and English struggle for possession of the city. You jumped whenever some startling little effect would take place on the diorama: a red signal flare shooting up from the ships on the river, a volley of shots crackling out between the lines of toy soldiers arranged on the green-painted Plains of Abraham.