Parents: help me parenting while separated (2)

[Ripe]

Yes, SunnyB, I will keep an eye on my kids.
Thank you so much for your input.

Yesterday, Monday, STBXW was still weak so she asked me once again to take care of the kids, which I happily did.
Today she is better so they are staying with her.
On Friday the kids and I are going for a long weekend.
Because for the last two weekends I stayed with the kids (this last Sunday and Monday only because STBXW was sick) STBXW asked me if she could stay with the kids until Friday.
S9 asked told me he wants to sleep at my place tomorrow, as it had been agreed previously with STBXW.
What should I do?
Of course I would like to be with my kids everyday, but I am somehow sensible to their mother's request.
But I also think this compensation thing is not very productive.
Not the kind of compensation like "you stayed xx days with the kids, now it's my turn to have them xx days".
But the one that my STBXW is feeling: being sick she could not have the kids so she must compensate for the lost time.