Ultimately your family is, barring WA coming through, the safest place for you. WA can still advise, and will have the best advice as to what to do moving forward, but its uncertain if they would be able to act immediately and you will still have the same issues about physically getting away.
Im sorry, your mind must be in an absolute whirl.
End of school term is close enough that you dont need to worry about that.
Other very practical things. Do you have money? Open a bank account like starling or Monzo, and get ready, as soon as you get to your parents, to transfer your wages straight over, or anything in your account. IF you dont he WILL empty your account, as he is named on it, and use money as a way to control you and force you home.
Did you ever check that the children's residency/ entitlement to child benefit is in your name? If you have proof of ID like a passport or driving licence, you can open a government HMRC app and check like that, if not you will need to call them on Monday. Do it first thing as soon as they open.
Put in a claim for universal credit. You work less hours and you have 4 children, you will be entitled to something. Do that online, you can put that in as soon as you get to your parents. You dont need to do the child maintanance yet, but that will be another step - they will allow you to be away from a home you own as they are used to this kind of thing, and if you arte not paying rent at your parents then you are not applying for housing element so you have that in hand for if and when that comes up.
these are the first practical steps.
I know you dont want the police but keep them in mind for when he starts to show harrassment - ie ignoring your requests to not contact you. If he turns up you need your father to tell him to go away. If he persists, then thats when you do need to call them. Its fair. you have given him a chance to behave decently and remain amicable, but he will have broken that if he doesnt respect what you have requested.
visitation etc can be dealt with down the line. For now just get safe and do not leave the children with him.nor, at this point, allow him to take them at all.