My council runs a council level Highland games/camporee every November. Bigger budget and support staff than for your troop, but the same general idea. Ann and John have provided great ideas that lend themselves to a smaller venue.
I agree each participant should wear a kilt. Either their own or one provided. Several years ago one of our scout mom's sewed about 200 faux great kilts (3-5 yds each of cotton/blend [read inexpensive] tartan cloth, hemmed) for the scouts to use with their own belts. Since the numbers now are around 500 we've added to the collection and the participants love it! It is quite something to see.
Good luck
Dave