I cuss around my mom whenever I would normally cuss in a situation period, I don't exactly swear like a sailor or whatever, but it's not like it's going to make her ashamed of me or anything, I just say what I say.
As far as it affecting what she thinks of me, it can't be worse than any of the other things I've done, if anything, the fact that I swear when I swear and say what I say around her shows that I treat her as if I expect her to see me as an adult, whish is a way of showing respect to her parenting of me, not hiding who I am or how I am, because I am me, and being her son, I would say that that in itself pays homage to her as a person as well.
I live kinda far away from her right now though... So, maybe one day I'll get to swear about stuff in her earshot again... Never know what the future holds.