I will never stop recommending this game, as it has a TON of couch co-op kid/newbie gamer content:
Star Wars Battlefront (2015)
You can regularly get it for $5 for the digital ultimate edition, which has all the extra heroes to play with. Even youngsters will know who to shoot as it's Star Wars, can be played third or first person, and the bot mode for Walker Assault is a 20 minute "holy shit I'm in the movie" experience that you can play co-op or versus, in split screen, getting to play as heroes or in all the vehicles.
It's legit the greatest couch co-op intro to gaming title you can get, and I will never uninstall this game.