Wondering if anyone had any advice

My 4 year old came home from preschool with chicken pox on Tuesday. We are due to fly to Menorca on 21st June. She will hopefully be ok by then.

But she has a 2 year old sister who hasnt yet had it.

Looking to maybe postpone holiday and rebook at a later date.

Can anyone give me any advice if we will lose loads of money or will we have to go through travel insurance (other daughter may or may not get them so we cannot provide medical evidence).

We booked it deliberately out of school holidays whilst the children are still young. Now it seems we are gonna have to pay extra and maybe cancellation charges to move it to later in July

Please please help!
Fi