My friend. Do not let this person into your home. If it’s not too late to back out now, explain that actually this won’t be possible, but you’re happy to chip in for a hotel. Then offer to pay whatever you’d have paid for the pizza and soda. If anyone has a problem with it, just be very apologetic but don’t actually explain why, you’ll just get into a debate. These people can’t force you to open your home to someone who you have been warned WOULD MESS WITH YOUR FOOD. Sometimes it’s ok to draw a boundary and stand firm, even if it means other relatives might be annoying. “I’m so sorry I won’t actually be able to help” keep repeating it. They’ll eventually forget and it’ll blow over.

Not everyone owns a washer and drier in their own home. In large cities in the US many people still have a communal laundry in a multi family dwelling or have to use a laudromat.