You can call me Mom, or Nicole, or whatever

This past weekend Brandon and I took three of our kids and my niece down to a nearby river. It was one of the few beautiful days in Oregon and we wanted to get out of the house. While walking to the river a man passed by us with his dog and struck up a coversation. In the end he called Brandon, Dad, to my son Hayden, who just stood there not knowing what to say. This keeps happening in our house. Even though our kids are not all related we do all resemble each other. When people find out that we are a blended family they try to guess which of us is related to whom. So far, no one has gotten it right. I am often referred to as "Mom" when I'm with Chelsea and she always just looks at me like, "Does this person mean you or my actual Mom?" While it's no big deal to Brandon or I if the kids call us Dad, Mom, or our names it does seem to catch our kids off guard.  I wonder if there is a solution to this problem or if it is just something you deal with until the kids get comfortable?