All of my kids friends have always refered to me as "mom". The call my husband "Big Phil". The kids are 20 and 17 now, but it has always been this way. For years I have fed them, they have slept over countless times, spend summers in our pool, vacationed with them, and just spent time talking, I love these kids. They become like family. I think we all know the difference between "Mom" to your own kids and "Mom" to their friends. Its a wonderful compliment that they feel comfortable enough with you to refer to you as Mom.