if you want to do a little work before you give it to him, this is my suggestion. this is what i did for a long time, before i started really messing with my N5. (instructions for clarification, you probably already know how this stuff works.)
TL;DR: flash stock M -> root -> remove junk [-> unroot]
ive never actually unrooted so i dont know the process, but if you feel its a good idea...
INSTRUCTIONS:
- download and flash stock Android M from the google stock ROM collection. (hammerhead).
- wait until it reaches Startup Wizard and then reboot into bootloader.
- flash TWRP recovery.
- reboot into bootloader again.
- from recovery, flash SuperSU to gain root.
- reboot into system.
- after setting up the phone, disable first and then remove (titanium backup is my choice) any unnecessary app.
note: make sure the app is disabled. sometimes after you hit the disable button it just uninstalls updates without actually disabling it. the app will say Disabled in the app list.
note: you can filter installed apps in titanium backup by Frozen status so the disabled ones are easier to find.
- reboot.
- if youd like, here you could unroot.
- reboot and enjoy.
REMINDER:
removing certain apps can prevent basic functionality from working properly. trial by fire, i know for a fact that the system cannot run without the Google app installed. Google Play Services is another necessary one.
i feel marshmallow was a fantastic generation of android. i was always learning new things i could do. also, as a human with a father i feel he would benefit more from stability than from extra performance or features.
have fun, and be safe.
