We visited all of the campgrounds and falls 4 weeks ago. We only did a day trip but were scoping things out for a future camping trip. All of the campgrounds looked great to me and made me wish we were camping with the exception of the 90 degree temps.
Anyway...this late in the year bugs may not be a problem, but that is really related to weather conditions and patterns. It hasn't been nearly as wet this past month as it was in the spring. Also, while we there the bugs weren't a problem and we hicked around the island at the lower falls and picniced in the shade with 0 problems. Trust me, with my kids if there were bugs around I would have known it!!
Make sure you look at the description of the sites if you make a reservation as a few could be really tight depending on the size of your rig.