mj.reilly:Xander Greg
Xander Gregory
Xander Grey
or Xander Greyson
And don't spell Xander as Zander. Don't dumb it down for people. It just makes the parents look...just no.
All of this, but especially the last part.
I really dislike Kingston. It just feels kind of pretentious to me to name your child "King." But even if I liked it, I agree with the PPs that said it doesn't flow well.
ETA: I'm generally not a fan of -son names, but I really like your reasoning for choosing Greyson.