I understand if you are tied to and prefer Davis, but if you want to consider something less expensive, why not consider Ambient Weather? The WS-2902 ($189.99) or if you want a fancier console and ability to add additional sensors, the WS-2000 ($299.99). The consoles for both of these stations can easily and inexpensively be adapted to 12V.
I am curious about your mounting plans. Will you have a post on your trailer that you will mount and dismount the array on each time you set up and tear down? Or a tripod? In either case I can see how leveling and north orientation could be a hassle every time you set up. I am not familiar with the Davis stations, so maybe they are more easily adjustable for level and orientation than the Ambient stations. I hope you will tell us when you decide what to get and how well it works out.
Also, are you wanting the array to be 12V powered? If so, the Ambient stations would not be a good solution as the array is powered by a solar panel charged capacitor with 2A batteries for backup. With a little creativity, I suppose you could come up with a way to power the array from a 12V source instead of the 2A batteries.