I would expect you already did or did not choose a DRZ by now, but here is my experience.
This particular bike was sold as a Kawasaki model for a few years, too.
80 mph is pushing it, not because the bike will not do it, but because if the light weight they get pretty squirmy and are subject to head shake once you get over 75 mph. Passing a large truck can be a rather enlightening experience as the wind sheer can actually pick you up and throw you across the road.
The bike is also fully capable of popping a wheelie at 60 mph with an experienced rider.
There are some mechanical issues, not serious but need to be addressed up front:
The vacuum controlled fuel valve fails from the new oxygenated fuels, and will leak. Toss it and get a manual Pingle valve.
The automatic cam chain tightener is a real piece of garbage. Just like the Kawasaki Concours, this tightener will just keep tightening the cam chain until the chain fails. Toss it, and get the manual tightener from an aftermarket source - set it once and ride it for years.
The drive sprocket is mounted with a nut, it works loose. Remove the nut right away and clean the threads and use LocTite to remount the thing. I use the heat release type LocTite for the best results.
Tires suck on the highway! Absolutely no other way to describe the poor performance of the dual sport tires on the highway. They are downright dangerous if you ride the bike anywhere near its potential on the street. If you are going to street this bike, get the Supermoto version, it also has better suspension than the dual sport version.
The OEM luggage rack is a waste of time. It may carry an old style lunchbox, but that is about it. Go to Cycleracks,com and get one of theirs as it is not only considerably more durable, it extends out over the exhaust pipe and avoids the inevitable frying of nylon on the muffler.
The seat is narrow and can become uncomfortable after about 75 miles. There are good aftermarket custom seats that work for riding long distances.
Also, do not ride it yourself. The danger there is that if you do, you will buy one for your own use. They are slightly more powerful than the KLR650, much lighter, get better fuel mileage, are better built, and will run the wheels off most street and nearly all dual sport bikes.
A 3000 mile road trip is a breeze for the DRZ, just keep the tire and fuel tank size limitations in mind.
I installed a Clarke tank and it carries enough fuel that I am ready to stop long before the bike runs out.
Also, if your kid likes to hot dog it a bit, be aware that they will do right at 115 mph stock, and will out run most superbikes in a sprint in all but long straight highways. Around town and in most back road situation, with good tires, there is absolutely nothing but the few purpose built Supermotos that will even come close to its performance.
It is sad that Kawasaki dropped the bike when it had its falling out with Suzuki. As, if anyone took the time to ride one they would buy it.