I like there middle names better. if it was IsiahCarson and IsaacCaden it would be much better. I tihnk Brenda is really outdated and i cant see it on a four year old. Rebecca is nice though. :)
Carson and Caden sound too matchy for me, and I'm not digging the same initials thing. None of the names are that bad, but I don't think Carson and Caden go with Brenda at all. The boys' names are trendy and the girl's name is dated.