Career with young children. PLEASE READ

So I have an almost 2 year old and a 2 month old and I'm conflicted over what I should do career wise.

Before I had my girls I worked full time in a private day nursery, which I was good at and was in talks about being promoted to a room leader. When I had my oldest I left as it made more sense financially.

I've now been offered the opportunity to go back to college and work towards the career I've always wanted (midwife). The training would be 2 days a week and my kids would attend nursery on those days.

My dilemma is this, do I accept the training opportunity and learn something completely new or do I go back in to the job I already know and am good at?

I need to think about what would be the best option for my children. The new career would include a couple of years training and then working long shifts, nights, weekends and holidays whereas the old job would include training days every 3 years, no weekend, no nights and holidays off.