Tom, I'm doing the same thing at my new property, only going even further away. I plan to put the tank at the gate so the propane delivery truck doesn't have to enter the property. It's the heaviest truck that would come on a regular basis, and this way it won't tear up my driveway. Also, they'll be able to deliver whether I'm home or not, and I won't have to give them a code for the electric gate.
It's going to be about 600' from the gate to the house, and then another 200' to the barn. Like you said, that's no problem if you size the line properly. Around here, we use polyelthelene tubing for the underground stuff, so it won't even be very expensive. The lines won't have to be huge, because it's normal to install a first stage regulator on the tank and run at fairly high pressure (around 20 psi) back to the house, then install a second stage regulator to drop it to usable pressure (11" WC, approx 1/2 psi). I'm also going to install a tee and a regulator every so often on the line in so if there is enough $$$ left after the house is built, I can install 3 or 4 gas lights on the driveway. It's too expensive for me to run the gas lights all the time, but they'll be neat on those "special occasions".
I don't know whether I'll have a buried tank or above ground. While I was in the propane dispensing business, I made good friends with the state LP Gas inspector, who stumbles across good deals on tanks from time to time. He has a 1000 gallon tank with a refill station set in the bushes near his gate which he got for free; I have my fingers crossed for something similar. I'd like to have the dispensing station (pump, meter, hose and nozzle) so I can refill my own RV, plus 20# cylinders for mosquito magnets and grills, at the delivered price - a lot cheaper than paying someone else to fill the tanks. You probably have something like that at your business if you refll fork lift tanks.
If it's underground, it will be between my driveway and the entrance fence. If it's above ground, it will be just inside the entrance fence, set in landscaping brushes, and the delivery guy will have to lean over the fence to fill it.
Attached is a picture of my unfinished and yet-to-be-landscaped entry; the tank will be to the left in the picture, on one side of the fence or the other.