I would be concerned about closing speeds, especially if there will be some exotics out on the track with you. In order to minimize the possibility of any incidents, make sure you practice good track etiquette, i.e. - pointing faster cars by, giving them the point-by early, not making any unpredictable movements, etc. If you think that there's even a remote chance that somebody might try to force a pass in the braking zone, then make sure there's plenty of room to let that car by, even if that person is blatantly breaking the rules of engagement. Different organizations have different tolerance levels on this kind of behavior so this may not be an issue with the group you're running with.
I wouldn't mind tracking my smart for a session or two, but I would definitely get very tired of it very quickly. IMO, the smart is more fun in an auto-x setting than at DE's. If you're used to faster and better-cornering cars, I bet it will get pretty boring after the 2nd session.
Have fun out there and more importantly, be safe!