I cannot accept that this is it.

[Mozza]

I had a slightly similar situation: my W needed to work (from home) on a holiday and asked if I could babysit the kids. I hesitated a lot because I would have been pleased to see the kids, but I didn't want to save her from her decision to go at it alone. In the end, I told her I needed to work too (true) and I let her hire a babysitter who brought the kids to my apartment. I worked from home part of the day, then at the office, and saw them for lunch and dinner, while she paid a babysitter (and worked unpaid!). I looked flexible, but not a doormat. I might need her too one day.