They're rated 18 for a reason and I'd have a problem with my kids playing or watching stuff thats not suitable for them.
how old would your kids have to be to let play\watch an over? Just out of curiosity.
The oldest girl is 15 in a month and she's just started watching 15 rated films, she dosen't play consoles she's happier coming ferreting than vegging in front of the tv tbh.
When you have kids you get a grasp of there mentallity, some kids are naturally more mature than others and you as a parent use your own judgement.