thanks for the great ideas!
Maybe since it's boxing week (thank goodness for a whole week of sales instead of just one crazy day!) I can get some foam mats for cheap. We planned on studding and drywalling a piece at a time, aiming for every weekend if we can.
Honesty will be key, hopefully parents can get past the unfinished part, and know that it'll be done ASAP. Fingers crossed!

Any more ideas are welcome!