One nice thing about that DC-to-DC with voltmeter is the screw-terminals on input and output.
Actually, this being a discussion forum, I was on eBay today and couldn't believe it - an LM2596 DC-to-DC (no voltmeter) for a whopping 38 cents (free shipping from Asia)! 
So if you don't mind a bit of soldering, you could pair this with a 99 cent 2-wire DC LED voltmeter to shave a few more nickels! 
Or, at 38 cents for the regulated converter, you could use 2 modules with 2 different voltages and have a switch to select from 2 voltages to provide high/low brightness with the separate voltmeter monitoring just the voltage to the buildings. Just saying!
But allow me to again get on the soapbox and lament my frustration in finding a practical/economical solution to the microscopic screwdriver adjustment of the blue trimmer potentiometers of these LM2596 modules. Maybe it's just that I long ago lost my teenager visual acuity or my dexterity with a micro screwdriver...
There are so-called "long knob" trimmers that you can finger-adjust (no screwdriver required). But there are minimum order quantities in the 100's or 1000's and different modules use different values (e.g., 10K, 20K, 50K Ohms). Agreed; most guys set-it-and-forget-it...but wouldn't it be nice if the modules came with long-knob trimmers!
