I can imagine they would be.
Three kids are a HANDFUL, especially at those ages. If you have health issues, you wouldn't be doing her any favors by pushing yourself past your own limits. You'd be no good to her dead - or hospitalized
I only had one child, but I had no support from anyone. My parents were very much in his life, but they were getting older and needed a little help themselves.
I was fortunate to have a job that could support both me and my son. I was able to pay for daycare while I worked. My parents got the occasional overnight/weekend day - just enough to "play" with him, then hand him over when they got tired. I spent a lot of time there anyway caring for them, so they had plenty of time with him.
It's a shame that deadbeat dad can't get off his tush and learn how to be a dad. If he can use his tool to make them, he can find some tools to care for them. But, hey, I know how it is. I couldn't force my son's dad to be a dad back then either. He stepped up to the plate later in life, when my son needed him most, so it worked out okay.
What I find ironic is that a mother of three is not qualified to work at a job caring for children.