[SalesForce] the best approach to mass create records from a button click

There are some tried and tested patterns for doing this, but if you'd like to save yourself some work and get extra functionality at the same time, you might want to check out Skoodat Relax. Skoodat have built a package up on the platform specifically for scheduling batches with as much power as possible and it sounds like a good match for your needs.

Otherwise, the limit of five jobs is being increased, and you can take the approach you've suggested. Depending on the exact details of the job you're running, you may be able to leverage triggers to do the processing on the other objects and just run the batch on your main record set.

There isn't really any problem with what you're doing. While you could set something up via Apex REST to support direct execution of methods without having an empty page, an empty page isn't a problem.

The one thing you do want to be aware of that whoever told you to avoid empty VF pages may have been referring to is that you can easily introduce a cross-site request forgery (CSRF) vulnerability if your page is doing something that an attacker would be interested in exploiting, like inserting/deleting records. This is something security reviewers care about, but frankly within a single organisation in an unmanaged package, it's usually a tiny risk. If this is a concern, the SFDC-recommended way to prevent this is to introduce a confirmation page in your VF where the user must click a button that triggers the action. All form posts in VF include a CSRF token which prevents CSRF attacks.