All these screen things are so addictive that it takes a strong parent to fight them! We had to restrict our son to so much 'screen time' per day. Now he is unrestricted because he has got into things like rugby, cricket and Morris dancing and spends a lot of time on homework so it's less of a problem. Our daughter was never quite so attached to these things as him. Didn't even watch tv much, though lately she's started doign that more than I'd like so we may have to bring in restrictions there. It is quite difficult to enforce these things though, when it's so easy just to leave them alone and get on with it.
If I were you I'd find a tactful way of saying the games should be left at home. They need to be taught that, if nothing else, they are anti-social and should only be played with in their own homes