I think it's tough being a single mother when the father of DC remains involved but unreliable.
And like others I thought at first you'd just send the little ones in a random cab. But I now understand that not to be the case.
So if not random cab, I think you were in a tight spot and had to try and keep all those balls juggling up in the air.
Not ideal, but I do get tired of the 'kids first at all times or you're a monster' type attitudes. I put my child absolutely front and centre of every decision I make. Which includes me having a secure job.
As my child deserves a home, and heating, and food.
So if the choice was, risk losing the only source of income in our family, or risk unsettling my child a little bit by delivering her/him to nursery in a different way... When it was a driver approved for school journeys who I knew well and who was happy to make a paid detour, oh and she'd be with her big sister the whole time too.
Well, call me an evil child eating boogeyman, and yup, I'd take the job, home, food for my children option please!
If of course you have a very secure job and an employer who was very relaxed about lateness and child care emergencies, and if you weren't on your nearly last strike having had no other problems in the last 6 months or so... Then yes, it wasn't a great choice.
If you're really struggling, I'd use this as an entry point to possible support.
Good luck whatever you do.