Ok just your thoughts on this pls?

Ok well i have been dating/in a relationship with my bf for 2 months now and he has now said that one of his girl mates that he has known for a long time has asked him to go and stay at her house having a few drinks with 2 of their other mates but its only my bf staying there i have tried to detour him from the idea but it just says we are just good freinds nothing will happen i am with you and you only. But i am not to sure about it. What do you guys think should I accept that he stays round there or say to him him if he stays that that will be the ned of us? Your advise would be greatly appreciated. Thanks.