How do I remove lock & suspend from the cog / gear menu?

I'd like to remove the log out, lock, suspend and switch user options from Freya's cog / gear menu*. To help my elderly relatives who seem to be confused by a choice of more than one.

I've already removed / disabled the log out and switch user options. I've also disabled the shutdown dialogue box. Does anyone know how I can finish the job by removing / disabling the lock and suspend?

Thanks for your help.

Thomas

* Sorry if that isn't the correct term - I've looked but have been unable to find the proper title.