Should he approve of their playing cards so that they will not go to dance halls and clubs?

We are receiving medical treatment in America, and we are living in a residential complex with approximately twenty families. We do not have a mosque in the complex, but one good person has rented one of the apartments for one year to be used as a musalla (prayer place) where the brothers can meet and socialize and organize lessons. After finishing ‘Isha prayer, some of the brothers – may Allah guide them – play cards in this apartment. One of the brothers told them off and said that it is not permissible to play cards at all, let alone in the musalla. But one of them responded by saying that if they did not play these card games, they would have too much free time which would lead them to go to immoral places such as dance halls and night clubs. Please note that some of those who play cards attend Fajr prayer. We hope that you can give us a fatwa on the permissibility of playing cards in this rented place in the situation described here. Is it permissible to play cards in a place like this musalla which that doer of good set up for prayer, meeting and remembering Allah? Is it permissible to sit with them when they are playing these games, or is it essential to keep away from them?.