Pushing updates to my Tablets?

Ok, so let me tell you some information about my situation first.

I recently have made a deal with a manufacturer of Android Tablets.
I want to be able to develop and add features & fix bugs and push the updates to my customers Tablets and have them be able to easily download & install them. The Tablets currently run stock KitKat 4.4 but I can always ask my manufacturer to install certain modded software (roms?)

Thanks,
Ollieorange