when I started my "secondary" relationship with my boyfriend, I got pregnant from my husband a few months later. For me it was clear from the beginning that my boyfriend would be just another important person in my son´s life, so I asked him to be his godfather.
My son is one year old now, and we have all benefited a lot from the situation. My boyfriend helps us alot when he´s around, and enjoys being with the child.
So I think, if there are healthy relationships, there is a great chance to make a child´s world even richer, with more people caring for him or her in different ways (and, by the way, learning to be tolerant about the different kinds of people).
The only thing I ask myself is: How do they explain it at school/Kindergarten? Do you have experiences with situations like, your daughter mentions "mummy´s boyfriends", and you get some reactions to it?
* Every new love enlarges the heart *