First, are these MS Office files? There's a few mechanisms within Office that will allow you to easily set up what you are looking for.
Beyond that; are you running any sort of directory service? (Active Directory, perhaps?) That would make this task very easy to setup.
Otherwise, you could set up several local accounts (to be used by remote computers) and set up access right via those accounts. Using that, those two people who can make changes would connect to an account on your computer that has read/write access while everyone else would connect using an account that only has read access.