Failover internet between two Sonicwall 2650's
I'm doing some tests with Sonicwall 2650's at two sites a mile apart from each other. Each Sonicwall has a WAN interface going to their own fiber internet connection, a LAN interface going to the LAN, and a LAN interface going to each Ubiquity AirFiber antenna which connects the two sites. What I'd like to do is if internet goes down at one location, the LAN hosts are then routed through to the opposite side's internet connection.
I'm looking at the failover section, and I like the features and load balancing, but is using this feature feasible even though I have to point it to a LAN interface(The antenna), since it wants a WAN interface? or should I strictly be using routing policies to set this up?