Why not throw in some classic TV challenges:

Set up a conveyor belt - turn off the tap water. Send out shot glasses (or dixie cups) of drinking water that the house guests have to put into a bucket or pitcher.

Run it slow enough at night that one person can keep up. Quicken the pace at random times so that you need three or four people to keep from having a mess

OR:

Fill the pool 1/2 full with marbles. Have the house guests get the marbles out of the pool.

OR:

Blindfold Challenge: Two houseguests not sleeping have to wear an eyemask at any given time. Guests figure out themselves who
will wear it.

OR:

Fun with Electricity: Complete a low volt circuit by holding hands. (this is a 4th grade/Bill Nye type of experiment) Make the circuit long enough so that all but one (or two) of the houseguests has to maintain contact by holding hands. Once the light goes on (signifying the circuit is complete) it has to stay on for 12-24 hours.