Guys, it's only a gimmicky display. It's 4 m up in the air so there is no oportunity to interact with it this year. I've also got to make a 60 cm diameter rotating Earth globe with geostationary satellite out at 2 m; a 150 mm moon to be positioned at relative scale about 18 m away; stands on refraction of light; polarisation (why do fishermen wear sunglasses but pilots don't), colour perception and the human eye; physics of sound with tubular bells, electric guitar, sine, square and triangle-wave generation and display on oscilloscope; and several other things. If I can get the planes to fly in a circle for two hours at a time in the morning and afternoon then it's a win!
Thanks for all the interest and suggestions. @Robin Colbourne gave me the correct terminology and a practical setup reference which saved me a lot of development time. For me, "pretty good" will be good enough.