First, I do not have the custody issues you have. But prudent flexibility in regards to time together is a good thing.
I think it's great you two worked out a way for your son to be with you. It comes down to shared flexibility. Having time alone with your son also meant she had time alone with your other son. It was a win/win. And kids having alone time with a parent is very good.
Automatically having to give up a your or her time with your child the following week goes against the give and take of being parents. If there's an exception to the custody schedule, it doesn't mean losing time the following week.
Flexibility allows for those tweaks in life. If one isn't willing to be flexible, then the official custody schedule goes into place.
Things come up. Kids have have all the say they want, but they don't make the final decision. That's the job of the parents.
Flexibility breeds flexibility. Kids are not possessions.
