I’m a physics teacher. You can DM me if you want ideas. There are there a few ideas that are easy to make :

• Elephants toothpaste (hydrogen peroxide + yeast)
• Bubbling witch liquid (vinegar + bicarbonate)
• the flaming hand (gas for lighters + soap)
• a simple acidic/basic reaction (red cabbage + vinegar + bicarbonate)
• turn off a candle without blowing it (vinegar + bicarbonate)
• make a water powered rocket (plastic bottle + bike pump)

Those are all very simple and inexpensive. Exception made for the flaming hand which can be dangerous.