We had a group of 14 go to
Welcome to Karri Valley Resort for the long weekend, was pretty awesome.
Three Bedroom Chalet - Karri Valley Resort
Worked out to about $40 per person per night after we got 2x three bedroom cabins. for $10 a day you can take out their canoes etc.
Theres not much to do there, but its a freakin awesome place to chillax.
Its about a 3 hour drive iirc