Chicken pox

So, I found out yesterday that my son has a chicken pox. We have fly scheduled on Wednesday, i don’t really want to rebooking because of the price (almost 400£ and i paid for tickets 100£), also I don’t want to put on risk other people ( worst scenario i rebook tickets) I would like to ask, how long takes yours children to get better? He had no symptoms at all, and rush is one big surprise.