I agree with the general responses so far the 17-50 f2.8 lens if you bring only one. In the early 80's I was a balloon pilot and excessively photographed many events and passenger rides here in NJ. Along with my FA body, my go to lens was a Tokina 28-85 f3.5-4.5, when practical I also had my Tokina 80-200 f2.8 on hand. Considering the crop factor of the DX format the 17-50 will yield you a very similar 25.5-75 range with the added benefit of being a faster lens. At this time of year, and specifically due to the turning of the leaves, most balloon pilots will primarily be doing "tree-topping" where you will fly at or near tree top level, this allows you to get some interesting perspective shots as well as pick leaves from the trees. Once you get above 100-200 feet everything pretty much looks the same, small. Plus it takes a lot more fuel to climb higher. The pilot would rather give you a good ride near tree-top level to a few hundred feet than a shorter flight at 1000+ feet. By FAA law and safety, you will have to land before sunset, the balloon has no lights to alert other aircraft that it is there. Depending on wind and landing spot availability, you will probably have landed at least an hour before sunset. The pilot has to allow time to pack up the balloon and if practical an after flight drink of champagne. The 17-50 will also come in handy for some after flight celebration shots. If you are near the Delaware river or some of the area reservoirs, and the weather and wind direction are favorable. The pilot may perform a river dunk or "splash n' dash". The pilot will bring the basket of the balloon to just above or resting on the water surface, before climbing back up to altitude. This is also a good photo op for friends or family who are tagging along with the chase-crew (also a lot of fun)
Pre-flight you can get some great shots of the balloon inflation. Before they ignite the burners and are filling the envelope with air (via a large fan), ask the pilot if you can take a few shots up inside the envelope from the opening near the basket, or through the vent at the top/ or side of the balloon. This is especially striking if the sunlight is filtering through the nylon. Sometimes the pilot may also take off his shoes and walk around inside the envelope while it's being filled with air. This is also a great shot opportunity, getting the seemingly small pilot walking around inside the balloon.
Have fun, looking forward to seeing your shots! I'm attaching a couple of scans from Fujichrome I took with my FA and 28-85mm back in 1981