You could add the water park and more option (the last time I got it it was $55 no matter how long your tickect was for--but I don't know the current price). It gives you one entrance to a water park, Disney Quest or (somethign else sorry, I forget what) for each day of park tickets but you do not have to use them the same day. So you could buy a 6 day pass plus the waterpark and more option if you wanted to spend 5 days at only a water park or only Disney quest (no thanks). But for the minimal cost that gives you something to do on your off day (you may want to go to both a water park and Disney Quest) and the option of spending part of some park days at one of the places as well.
All of that said--we like to take a day off in between to enjoy the resort hotels, swim, etc.