A Fourth Birthday Knight Party. Loving the balloon idea. Maybe have pool noodles around the stakes, then tie the strings around, so each "team" knows where to start? You can make the horses from pool noodles too.
This is a large castle, and is a nice, very late-game house. The grey represents what material you want to make it out of and (not including floors) is approx. 40 stacks of material for an 10 block high, one floor castle.