You're young, no longer enjoy your job, working anyway and you obv have the skills to look after all your DGC, so it is definitely worth considering if you don't mind the decrease in wages. Maybe you could change your job to childminder while looking after them, until they go to school, with the potential to take on another child?
Clarify now anything that worries you, such as pensions, if you're ill, being self-employed etc. It's the 'other' times that need to be clear too - late night working?, babysitting etc. You might have a different view about doing those things. Also the 'rules' DD has might make things more difficult for you. They are near though so that's a bonus, surely you can all eat at their house or ask her to pack up lunch for the children. Set up a direct debit so money is never an issue between you. Whatever you decide, hope it's all resolved amicably for you.