Active-Active Virtualmin servers

I have searched and not found answers(maybe my google skills are lacking) to my question of how to set up two virtualmin servers such that I can use a load balancer to round robin between the two, more for availability concerns than load concerns at this point but will soon (hopefully) become a load issue also. The hope is to be able to scale this to more than two servers in the future. I am planning to have separate physical boxes for MySQL’s in a master-master replication mode so not so much concerned with that portion. The Virtualmin servers will be primarily for eCommerce sites running magento, oscommerce, zencart, wordpress, joomla, … All servers will be local to each other in the same DMZ/network segment. I will be using pfSense to round robin the traffic and already have this working well with several Tomcat servers.