Install Mountain Lion on different Macs with different Apple accounts I'm pretty sure that the title is unclear, I'm going to explain it:

We have to update 11 Macs, so we bought 11 copies of Mountain Lion (from the online store, not the App Store) and we received the Redeem codes.

We have just a little doubt, we don't know if we can download just one installer and use it for every Mac we have or we have to download the installer (via the app store, using the code) for every Mac.

Can you let me know?
If the machines are on different iTunes accounts then it is possible to do one download and install it on all of the machines. Before you run the first installation be sure to copy the "Install Mountain OS X Lion.app" to another folder or disk.

To install on other machines you can follow the instructions provided at Ars Technica.