It is said from the shinever Rov that naming a child after grandparents is a segule for a long life.
You AND your wife are give a spark of Ruach Hakodesh when it comes to the name, so don't let anyone bother you about it, they weren't granted the Ruach Hakodesh so the can only damage!
You may not know it, if it's your first baby, but one doesn't wish Mazel tov until the Placenta is out.
So, good luck and let us know when we can say...