Adding to the above, makes costumes out of any of these:
1. Bubble wrap
2. Hollow plastic objects threaded together that can clatter when you move
3. Inflated balloons
4. pots and pans (played with wooden spoons)
5. Shoes made of boxes filled with rice

Process the microphone with different audio effects (reverb, distortion, delay etc.)

Build some DIY speakers using magnets and copper wire and try using different resonating membranes

have a person/people walking around with a microphone, amplifying the building activities

Try to make the drum kit from materials that you find and that cost 0 money (trash, recycling etc.) - Wooden spoons are still essential