I need a nice but firm way to get people to stop insisting we throw a party when we are sick?

I was supposed to have a Halloween party on Saturday but my family all has COVID (tested positive between Monday and today). I'm really exhausted and my kids and hubby are miserable.

I'm really not feeling the Halloween party. On Tuesday, I sent out a note to everyone invited. I said that since we all have COVID, we're not going to have the party. A few people said thanks for letting them know but now I'm getting some people who are like "Oh have the party still! You'll be fine. It's just COVID. Who cares?!"

I said that we're really all quite sick, but at least 5 of the 30 people are insisting that we still do the party. I said we're not feeling well and way too tired, but they keep saying that we'll be fine by Saturday.

What is a nice, but firm, way to say the Halloween Party is not happening? I already said "I know you were really looking forward to this but we are absolutely exhausted and we don't have the energy to host. If you want, you can come pick up the decorations we have and the food we bought and you can do your own party!" I really don't know what else to tell people at this point.