It would have been nice yes if they had mentioned something upfront but at the same time if they listed and sold in 5 days then they have been very busy and distracted and it may totally have slipped their minds as in it was no longer something to mention in passing that the house is up for sale. Once sold they are in the position of having to know their plans and yes they need time to digest it all. They may or may not have a house already. Many list thinking it will take awhile and use that time to look for what they want. Their time line has just changed that is all.
I have had families move and not share the news till they know what is happening and that is their right - it is a private matter to them as long as they fulfill the contract terms.
If they find a house where the drive is still convenient then child will stay. If not they will move her.
At the same time all of this is really a mute point isn't it in the sense they asked for a change in hours and you said no so in a sense you have both given notice to each other - just not determined the timeline of when it all happens.