Admin (not user) access control

I want to have a post page on an otherwise static site which contains village information. I want to allow authorised persons (in this case secretaries of village organisations) limited access to post announcements which can be seen, and commented on, by all users, and to edit their organisations static page. How do I give them access to the posting page and their static page, but restrict them from admin access to other pages.
I found a few plugins that may do the job but I am not sure if they would nor which would be the best given my needs.
I’d be grateful for suggestions.