I think managing childcare is one of the most difficult aspects of midwifery. I truly believe it takes a whole community to support a midwife and her family. I had a list of folks who offered that I could call them if I was in a pinch and needed childcare. If my husband was unavailable, then we had a list of close friends we could call. In most cases this worked well..not to say it was easy. My first son does not take transition well and still does not go to other people with ease. I feel lucky that my husbands work schedule is flexible, he is self employed, but know this is not the case for many other midwives.
I do know some midwives' who have found a way to work with their children (when they are young) bringing them along with them to births. Of course this does not work for every client, or even every child. But just to mention, they worked it by having a local doula attend as a childcare provider, they paid them some amount and also traded midwifery education and the chance that they might be able to be involved in helping at the birth if the child were asleep or otherwise entertained during the labour/birth. But they did have it very clear, that they were there first as a childcare provider.
It seems impossible at times to figure it all out with kids, especially when training. For myself, I decided that when my kids were young they had to come first and so I always took at least their first year of life off call. I think local grandparents would be a wonderful option, especially if they are retired and have a good relationship with your children. I'm not sure of your situation. I do hope you can find a way to work it out. I have often fell back on the fact that there will always be pregnant woman to work with, yet my kids will only be kids for a moment in time.
Good luck to you in finding a solution for your family!