Hello,
I am a Full Stack Web Developer and I have a very good solution for you.
Your website have all the details so It means that you have a database where these details have stored.
Now first you need a API to communicate with your database directly and in a secure way. Now the websites will run on your API, they will make a call in order to retrieve information (details) from your database every-time anyone opens the websites. so if you edit something now and then someone opens your clients website the change will reflects.
I hope you understand it.
This project can be made in 500-700 USD, depending on the features required.
Thanks
Meeshal k