DH has a very fixed defined contact order. It's very fixed because due to her mental health issues, ex has a very chaotic life and used to constantly change contact arrangements.
We are going away in a few weeks and have let her know that contact can't happen, but due to recent health problems, DSS has missed a few weekends so DH asked if she would consider changing the contact, rather than DSS having to miss it.
Ex has replied with a letter that says she will allow the swap if DH agrees (and signs a statement for 'evidence') to swap any contact that coincides with any family celebration. She has about 18 dates in mind.
Just wanted to get feedback to see what other people thought.