Choosing a Saint...

My RCIA teachers want us to choose a Saint to be named after for our confirmation...I am thinking Mary...I asked my teacher if it was ok to choose her...I mean, she is Jesus' mother...she said it was fine...I was going to pick St. Helena...Constantine's mom...she inspired her son to become a Christian and he made it the official religion of the Roman Empire...which quickly fell shortly after...anyway, I am digressing :) I decided on Mary though because I have been praying to her and I have seen changes in my life...I am building a relationship with her and it makes me very happy...but, I am not sure how this extra name works...anyone done this? I guess kids get these Saintly names when they are confirmed as teens, right? Where does the name fit in with your birth name? After your middle name? I want to start teaching my daughter about the Saints...so she can find one or two that she can pray to as well...and find one to be named after...what Saints are popular with kids?