Or you could sign up for my Nature Forward Butterfly Boot Camp: Confusing Fall Skippers
For diversity, it's hard to beat HoCo Conservancy community garden. I was at the Glendening Preserve Plummer House butterfly garden yesterday and there were about a million skippers, 99% of which were Sachems in all their infinite variety. Other diversity was low, with a few Fieries, Little Glassywings, and one of the "witches' I'm still working on.
We'll probably stick closer to home for this field trip, either the National Arboretum or Glendening. Downside to Glendening is that they no longer permit net and release (or capture of ANY kind) so participants can get a closer look at diagnostic marks. On pain of banishment from Jug Bay.