If anyone in your family is a member of any organization call them and see if they have any codes. We use a construction association code (company is a member) and we paid 149.00 for a night in a basic family room. Room is fine as it has two queen beds and a queen pull out, fridge, microwave.
Alternately, keep going on the great wolf web site and plugging away. I found an uncoded 129.00 rate once so they are out there. Note that great wolf has caught on to people sharing codes with others and we got pushed for ID last time when we checked in. Since our organization doesn't have little membership cards this presented a bit of a challenge.
Cheap internet room rates are easiest to find if you want to go mid week. We got a great one for a Sunday check in Monday departure as my wife found out all the school PD days well before the school year and we booked it before everyone else clued in. The hotels have tracking systems that see when action is heating up on certain days and adjusts rates accordingly (basically same as the airlines who do it almost by the minute)
Last word of advice, the food is expensive. Take drinks and snacks for your room. You are not allowed to take outside food in to the waterpark (nudge, nudge!) and there is really nothing within walking distance of the park. Going downtown just puts you in over price tourist traps with huge parking charges. Go out Lundy's lane and you can find the fast food joints