Move Access Based Application to Web Based

I have a very simple access application that allows a user to input information and save into an access database. It was basically something I wrote to keep track of donations to a non-profit organization located at one site. Now we have 3 different sites all under the umbrella of the non-profit and they all are running seperate versions of the same access application. I am now trying to simplify the application and make it web based with a mysql database backend and thus allow those three sites to input information via a website that would go into this web application. Couple additions.....1. I should be able to give mutiple people within each site access via thier own login and transactions would be logged by login. 2. I should be able to create read only access for each account. 3. one site should not be able to see what the other site is inputing. 4. A master account should exist that allows him to see what is going on at all sites and make changes if needed. 5. I should be able to add sites as needed.