Thank you for that full explanation of your needs.
Yes, Foodclub will allow you to do one-stop shopping on all your local vendors, plus UNFI and Frontier. Several other clubs are now switching from UNFI's site to Foodclub because they don't like the new UNFI site, and plus they don't allow splits for their Western region customers.
Frontier's site does have slightly better product info and browse capability than Foodclub (for now), but it also doesn't do splits, though not a huge problem since many Frontier items don't require splitting. But also Foodclub will notify you of Frontier sales each month. There are probably other benefits of Foodclub over using the Frontier site, not to mention one-stop shopping.
Anyway, about your local vendors: you are correct, you will want separate private databases for each. The way to accomplish this is to create separate sources, and enable a private database for each one. See this topic on adding new sources:
http://foodclub.org/phpbb/viewtopic.php?f=774&t=1900Once you have new sources for them, I can give you a single global phpMyAdmin user which has access to all of them. So go and create the new sources (easiest is foodclub.org/admin using "Link to account id" and then Account linking), and let me know what phpMyAdmin user you want to have global access to all the databases.
Also, I am going to move this topic to the "Product database" subforum since it is about product databases.