My Hilary at age 11 illustrated how sound waves move. She constructed 3 tubes both the same length but different shapes. Air cannons she called them. Round tube 4 inches in diameter, square tube each side 4 inches, equilateral traingle tube 4 inch sides. On one end of each was stretched tight latex from punch ball. A cap on the other end (well sealed around the seam) with 1 inch opening of the same shape as the tube. In front of each cannon was strung a curtain of strips of tissue paper. And a mallet for tapping the latex end of each tube. The round tube is the only one she could get a sufficient poof of air to move the curtain.

What she was trying to prove with this experiment, I am not certain but it won a ribbon in middle school science fair.

Andie at age 6 designed a Back of the Bowl brush/mop thing to facilitate cleaning behind the toliet bowl, after she heard me griping about how the boys in the house lacked aim.

She received honourable mention in young inventors competition at her school for that one and my undying gratitude.

Your Morgan sounds like a corker. Hope things work out more favourably for you both on the visiting thing.