I put 75K on an '85 K100, probably the most dependable bike I ever owned. If it's been stored/maintained properly, It should be fine with the low mileage.
I would take the other folk's advice though and go ahead and replace a lot of the rubber stuff, particularly brake lines. The bike will also feel a bit "dated" compared to newer bikes, but they are rock solid dependable. The '85's also had more power than some of the later models. It really just depends on what they want to do with the bike.