We have hot air ballooning here also, and several times they have floated over the house pretty low, looking for a place to put down.
One thought that comes to mind, especially on the evening shots. These things are pretty large, and move around a lot while being filled. So if you use a shutter speed too low, you will have motion blurr. In order to get a faster shutter speed, you either need a higher ISO speed, a lower f stop, which translates to a smaller DOF, or better yet, all of the above with a tripod.
Using a wide angle lens, will certainly help with the DOF. Also looking at the hyper focal tables will give you an idea of about where to focus (and f stop), so that you can get quite a bit in focus from near the camera out to infinity.
... hope that helps - which gives me an idea - that I need to look into when the hot air balloon meet here happens.