Hello,
You're very welcome, I've always got a hug for a fellow student nurse. Nobody can fully articulate how tough this degree is. I also find that people aren't honest either, especially when they're struggling.
I haven't got the answers but, I've got a few questions that might help your thinking.
Both of your kids will be in secondary school soon, so why do you need childcare for another 6/8 years? Your mum is your mum - beg, plead and beg some more for her to help you with childcare.
If you take that job, do you think you'll be happy and fulfilled working in a nursery? Do you see yourself doing this when your kids no longer require childcare?
If you walk away will you have any regrets?
If you don't become a nurse and get bored/lose interest in the nursery role, what else are you going to do? Have you asked about transferring to child branch or have you decided it's too late? You might lose the bursary by changing branch, but the student loan repayments are negligible. I've still got mine from my first degree when I graduated in 2005 
Try and go back and remind yourself of the reasons you pursued the nursing degree. What did you envision your life would be like after qualifying?
Give yourself a few hours to make yourself a life plan - keep it simple. This is a snapshot of mine:
I want a career that isn't just about chasing £££ to make profit, I want a career that will fulfill my desire to travel and potentially work abroad/emigrate. I want a career that is mentally stimulating and includes progression/job security/ opportunity for further study until I retire.
- as a qualified nurse I will always find work in any part of the UK. And overseas if I do the conversion course.
- the nursing degree will be a stepping stone to other careers: teaching, research, occupational health, senior health related roles in public sector.
- I will die happy knowing that I was involved in an activity that put something back into my community.
"We have a little group of mature students and they all seem to think it's tough but all seem happy/excited for placement and seem to enjoy uni." - I'm going to call BS on this and say they're not being honest. Everybody in my group and that's over 100+ of Child, Adult, LD nurses are tired, ground down and a bit pissed off.
The 2nd year is the hardest year. All the lecturers, nurses on placement and mentors are prepped to provide a little bit of extra support for 2nd year students.
I think a lot of your problem is the isolation you're feeling. Come and join the nursing groups on facebook and post your questions. There's always somebody awake that will reply and give honest answers and solutions.
There are loads of student nurses juggling childcare and something always works out. I recently read about a student who has 5 kids, separated from her partner midway through the course and she works weekends at the hospital and she's determined to become a nurse. She is my hero 
The Facebook group is called student nurses and beyond.