I do this...
 

usually I save the entire first dances section for the extras (on packages that get hte extras section). otherwise they get a minute or two of each dance; B&G, bride & father, groom & mother, anniversar dance, etc.

I allways watch the movie together with my clients as well, mainly because they have to pay me right after that :D but also to check if it plays allright on their player. I also love the ooohs and aaaaah's :) but I don't do any corrections on the spot. Only if I mispelled something then I correct, but if the dvd plays fine then I consider my job done.

Currently I have one package which also includes the total footage of the day, it's often long and boring but some clients want it, it's just the raw footage without the addition of extra music an so on. Your option sounds interesting. The only problem I see in this is if they wait too long to send you the changes. If I would send a copy to them for review, it could take quite a while before they resend it, in the meantime I have to park the complete project somewere on an external drive and those tend to fill up real fast in that way. Adding the dance part in the evening completely as an extra on the dvd sounds interesting as well, based on the reactions I got so far this is often the most popular piece.