Thanks for pointing me in the right direction.
I fixed the problem of most of the administration menu missing and add/remove missing by ...
When grub starts choose the recovery mode option.
type sudoedit /etc/group
changed the line admin
:117 to admin
:117:andy save file, (andy is my sons username) reboot all fixed. Went into system, administration Users and Groups and re-setup his user privileges.
The problem with shutdown and restart missing from the Quit screen.
Go to system administration login window local tab
put a tick in Show Actions menu
Happy boy, who was even happier when I installed Scribus DTP and Abiword.