Hopefully, you'll never have to make this decision. In the interim, why judge someone else?

I disagree, the children ended up knowing the mother's mortality before she passed and hopefully had time to make peace before the end. The thing the children were deprived of was the years of slowly wasting away - I don't think witnessing that is a particularly strong experience.

And... I suspect they did help, I suspect the kids did more chores to keep the house up, doing things that the mother was too tired to keep up with. If it was revealed correctly the children could find comfort in the fact that they had been helping all along, they were just being shielded from the grief (and temporarily)

Most children don't get such an experience because their parents aren't terminally ill. I think you'd agree that's fine. If the mother weren't sick would it be a big mistake to not fake the experience for the kids' benefit?

I'd rather not know.