I would recommend them to play battlefield 1, it is a first person shooter set in World War 1, it has a campaign where you can play some of the most beautiful and heart breaking real stories from the Great War, and an online version where you can play even on the fronts that aren't portrayed more often by the media (like the Italian, Ottoman, and Russian front both against the germans and during the civil war).

It does a beautiful job because it teaches how war is at the same time an horrible thing and an intricate part of humanity, its actually really poetic from time to time, but of course, there is a big use of violence so I recommend it only if your kids are old enough.