My boyfriend wants to sleep over bm house on Christmas Eve! ?

Ok so me and my bf just moved into a home together .He has a 4year old little boy and he said that Christmas morning that he was going to go over to his bm house to watch his son open his gifts in the morning,ok fine . Now, it's changed to him spending the night at his bm Christmas eve! He says there is nothing between him and his bm so I shouldn't have a problem with it.. But, I have never met this girl and me and him have had trust issues coming from him and him being dishonest in the past. I think him spending the night is a little much. Am I being selfish or is he doing too much?