I met my DH when my son was 2years,3months old after an abusive relationship ended with my sons biological father. DH and I dated for a few months and the 3 of us spent a lot of time together and then within 6 months we moved in together and it felt sooo right. My son called DH by his name and then all of a sudden he started calling him daddy about 2-3 months after living together but we knew we were going to be together for ever and he loved my son from day 1 so we encouraged him.
My ex wanted nothing to do with him and hadn't seen him for a year and then we went through family court, he was granted visiting rights but decided at last minute he didn't want them. We sat down DS and explained to him he had 2 dads but when you are dealing with a 3 year old its not that easy if there is no one there to reinforce that, so he didn't even think about it and neither did we until DS turned 9 and my ex showed up and decided he wanted to play dad again.
After 6 years of not being around,no contact of any sort, we had to sit our DS down and explain to him he actually had 2 dads and he has been seeing him now for nearly 3 years.
When he found out his exact words were" I never knew dad wasnt' my real dad, because my DH loves him and treats and cares for him exactly the same as our other boys.
He calls his biological father by his name and calls DH dad and thats the way we all like it because he is his dad, he has been there for everything and always will be.

If the father is in the picture and he continues to keep up contact,phonecalls, letters, visits etc then your daughter will know him and she will grow up knowing she has a father who loves her and if everything works out with your boyfrind then she is lucky as she will have 2 dads that love her.
If your ex is a nice person and someone she can look up to then you won't have a problem.
It is much easier when the children are younger to introduce a new person into their lives than when they are older.
Good luck with your decision and sorry if Iwent on a bit.
Take care
Michelle