Here is a list of things you should not forget to bring to onScene:
Got a vaccination certificate? Bring it!
Got a (negative) Covid-19 test? Bring it!
Bring your health insurance card. If you are traveling internationally, consider getting a travel insurance.
A demoparty will be a burden on your immune system. Power it up before and during the party. Bring stuff like Vitamin C, Vitamin D, Zinc, sea water nose spray.
Sleeping bag + blanket
Air matress / sleeping pad