Chuck,
I would encourage you to have plenty of easy to medium-easy dances available, and avoid programming all complex dances.
Consider an easy dance done as a no-walk-through, or with minimal walk-through, or with a focus on executing this one little timing thing well so the whole crowd can have success with the dance. There is a reason for it to be in the program, and a satisfaction with doing it well.
So, yes, pepper the dance with complexity, but don't make the whole recipe taste like pepper.
Complexity can include: unusual formations, unusual figures, unusual music (outside the 32-bar structure, for example), unusual interactions (shadows, or same-sex swings).
Also, consider using dances with figures that are unusual but not difficult (ex: circle right). This puts experienced dancers out of their pattern but does not unduly strain them. (It also puts beginning dancers on even footing with experienced dancers, when you use this technique for regular dance evenings).
Good luck, I'm sure it'll be fun!
--Jerome