A modified version of tug of war. Balance discs and half noodles are all that is required.
To stay on you balance disc while attempting to move you partner of of their balance disc.
Have two participants on balance discs about 2 feet apart. Have each person hold onto one end of a half noodle in each hand. On the signal the participants will push and pull on the noodles to try to knock their opponent off of their balance disc.
If this is too hard, give each participant two balance discs, one for each feet. This will allow them to be more stable.