I appreciate advice like this is well meaning… but if you don’t know anything about social care or fostering it really isn’t helpful.
You absolutely can’t hire someone to go and discuss the intimate and complex needs of the children you are caring for on your behalf - or to undertake the training in safe care, attachment, trauma…
Social Workers aren’t just making the OP do these things for their own entertainment - they are legal requirements.
You also can’t just hire a nanny for children who have likely experienced significant trauma and loss and will still be working hard - even after a year - to recognise OP as their safe and consistent attachment figure.
OP, I wish I had an answer for you. Like the other poster above with professional experience, I do know of families who have been able to negotiate significant financial packages. I would also consider asking for a placement stability meeting to set out the demands of the children’s social worker, your social worker, the IRO, PEP meetings, health assessments, the family time plan etc etc and how they can work together to streamline this for you - but I can see it would be running uphill through treacle and I guess you have to balance how much energy you have available to give to that battle.
I so wish your employer would get more on board with allowing you a substantial period of leave - I think there’s lots of benefits for your identity, your pension, your long term prospects. But if it’s not going to happen, you need to try and get the absolute best deal you can from the LA.