Hey Bill-
Have you guys checked out Racing Adventures? They hold one and 2 day sessions at tracks all over in FFR Spec Racers, 'Vettes, or your own Cobra- they have some dates in September at the 'bahn in Joliet. Just FYI.
I have done Skip Barber and Racing Adventures- both are good in their own way, but being able to thrash a Cobra around a track has its definite upside!
I'm sure no matter what you choose you guys will have a blast.
http://www.racingadventures.com/
Best-
-John