I would take them. Though they don't know the deceased well, it is family and I know their presence would be appreciated. They're not too young. Death, even unexpected and sudden death, is just part of life. Better to treat it pragmatically for what it is now than for them to be emotionally blindsided in their teens. Just my opinion, of course.
Also, where it is a wake, not a service, I would plan on just going for a little while and then scooting out before they lose patience. If they can be calm and in control for 45 minutes, plan on staying for 30 minutes, then give hugs and go home.