14 Baby Platy
 

Are all still alive and doing well, wondering how many months I should wait before attempting to take some to my pet shop and move some to my adult tank... They where born Christmas morning...

They have to be bigger than the biggest mouth in the tank that might eat them.
As for selling to the LFS.... depends on the store... most want them a fair size. they also need to have a place or tank to put them in. Call ahead to see what or when they can take them.
Congratulations!!