Hi,
We have build this website using CRE loaded eCommerce cms..
Also, All three website build in same server so it easy to manage price update in main website.
We set Mass Price update module to change price percentage wise or actual amout deduction.
We are also able to data feed module for update database automatically in selected hours or manually update database.
Once it complete then upload in server for your review.
Any further discuss regarding this task kindly contact me via email.