Backup and off-site restore setup
Taking a backup from a slave is exactly how I do it, and it works very well. I can't imagine a better way to take a backup without causing downtime of the master and your application.

I am intrigued by your statement about not being able to restore a backup onto a mac osx machine (this could probably be a different question). An alternative is to setup a virtual machine on your local mac machines that run the same OS your production servers run. A tool that makes managing those machines easy is Vagrant.

Mimicking the production environment has the added benefit of allowing you to test any restore procedure with a fairly high degree of certainty that it would work on the production servers should you need to.