Hmmm, I share your scepticism about the "work ethic" argument.
I think our society at the moment is obsessed with the supposedly improving qualities of paid (or coerced) work.
When I hear people saying that by having a job they are providing a brilliant example to their children, I'm always a bit 
There are all kinds of good examples parents can set to their children. That argument can be used to justify almost anything.
It's just as true that a SAHP provides a good work ethic for their children who see them working all day to support the family, rather than just seeing them leave in the morning and come back in the evening.
For all the kid knows the parent who is out all day is sitting on their arse watching TV. (In my case, that is sometimes very close to the truth :o)
However, I have as little patience for the "kids want their Mummies around" argument.
Not all kids are the same. Not all kids like being poor and missing out on treats or cool holidays or interesting after school clubs.
I know I didn't. Although I guess I liked having my mother at home, I didn't choose to be a SAHM. And neither did my sister. My brother also works.
So either she gave us a great example of work ethic, or we didn't prefer her being at home all day to her working and us having more money.
Maybe you could try extending the same lack of judgment to parents who work that you want other people to extend to you?
Personally I think there should be financial support for single parents (or widows) to be SAHPs if they want to be. I think it is one of the good options for bringing up children.
I think, given that your children recently lost their father, that it is right that you should do what you think gives them (and you) the most stability at the moment.
I'm very sorry for your loss.