Muslin....dont worry the white floor isnt actually being used like that!
What age of kids is this for? Personally I'd use 2 front lights and maybe a floor light if I could get away with it.
Reflector balanced on chair will give you a very narrow shooting angle.
With such a big room I'd probably move the front light(s) further back and ramp the power up. This will give you a more even light across the area so if the child moves forward or back you will still be in the zone.
Oh and you know about taping the cables down, right?![]()