AlwaysOn Availability Groups - Proper Quorum across WAN
For this you would (hopefully) be using AGs in an asynchronous fashion (latency will kill performance otherwise). This means that you will not get automatic failover to your DR site, that's just something to be aware of. I would also, typically, not recommend using less than 3 nodes, but if that is not an option for you...

As regards quorum. You would want to use a file share witness + node majority configuration. Keep the file share witness in your primary site, on a server that is not a part of the WSFC (Windows Server Failover Cluster).

In the event that you need to move to your disaster recovery site, adjust your file share witness to be local to the server there. This will allow you to maintain a voting quorum in your primary site at all times. 

Just be very careful when performing patching of your witness server not to end up losing quorum.