I don't know a lot about used car prices, so if I were in this situation, I would check out comparable prices in the area and maybe on autotrader.com to see if it's a good deal. It sounds like it's been well cared for, and it is nice that you know its owners and have faith in its maintenance history, so if you find that comparable cars are around the same price, it might be worth it.
I see that the Passport is an SUV. In that case, I would also take into account the mileage difference between that and a sedan. Your son's gas costs are going to be higher in the Passport than they would in, say a Civic or a Toyota Corolla. Not necessarily a dealbreaker, just something to factor in.
But also knowing that it's an SUV makes it more likely that $1100 - $1400 is a good price. So there is that side of it too.
Why not fly to the location and pick it up and drive it back. Much cheaper than shipping it. It will serve your DH well for the next year and when he goes to college (room for hauling his "stuff" etc. If this is "too much " car, then he can sell it and apply the $ to something more suitable.
I think paying less than $1500 for a car that you know it's history is a great deal. Even though it doesn't get as great gas mileage, I would still get it for him.