To think a grandparent who hits DC can never see DC alone

He should never see them again. Supervised or not.

And if your own DH wants to place your own children with the same abusive man , then you have no choice but to leave your husband , whether you want to or not.

I'm going deep and fundamental. Speak with a therapist. Try reading Families and How to Survive Them by John Cleese & his psychologist pal.
This family issue is about power, control and loyalty. My heart goes out to both you and your husband.
His father may be very controlling. If so, it will help you to think of when you have felt intense fear yourself and imagine your husband experiencing that fear from early childhood. F in Law is not respecting the parents. He's not respecting his son. He's certainly not respecting you. He exercises power through controlling his son. Your husband doesn't realise he's damaging his marriage by his disloyalty to you. He must fear his dad's disapproval terribly...existentially? He's putting his dad before you and his child's safety and well-being. He doesnt realise because he's been shaped by a life of parental control.
If I'm right, do see a family psychologist. You need help to save a good marriage & your lovely family.xx

DH wanted us to leave DC with his parents,

He's a monster. He wants to leave your kid with violent child abusers. I don't know how the marriage can continue.
Have any of the abusers or their supporters been reported for their attacks?

Honestly, my child would never see a Grandparent that smacks children, never mind be left alone with them.

WTAF.
So you know your nieces are being abused and you are doing nothing to stop it?
I'm sorry OP but safeguarding is everyone's business. Find your bloody courage and speak up.
This has to stop and if you do nothing then you are complicit in it.

I would refuse to go - if I thought I’d have to put my child in day care in another country because I didn’t think they were safe with family whilst I was at work there is no way I would be going. What is your DH doing the month you are there?

You are being unreasonable going to stay for a month with DC knowing the situation, just stay away and keep your child safe.

That’s very true.

I would give the passports to my best friend to keep safe and refuse to go. I would also be tearing DH a new one over this.

Someone would have to walk over my cold dead body before I let them anywhere near my kids thinking that hitting them is ok.

Absolutely fucking not. I would
leave my DH over this if I had to.

Mother nature made mothers powerful protectors, that’s our most important job.

I would not be going, and neither would the children. Your DH is a disgrace. If he can’t manage the most basic part of being a parent - protecting them from harm - then he isn’t fit to have charge of them or make decisions for them. Get rid of their passports and refuse to go.

The less said about the “grandfather”, the better. 🤮

Can tell you from personal experience the conversation is unlikely to go well with your FIL.

can you refuse to go? I’d certainly have a stand up row with my dh and be very clear that if I went I’d be telling FIL exactly what I thought of him and shy he couldn’t look after our kid,

you may find dh does not want that and backs down

I’d tell (not ask) PIL and DH what was the arrangement.

I’d speak with daycare to ensure they are clear the child should not be picked up by anyone other than you or DH.

I tell DH that he if leaves DC with his parents I’d be leaving him permanently.

Ask your DH why he is scared of his father…..

I’m pretty sure the answer is obvious. If he doesn’t want protect his own child from that he’s despicable himself.

Honestly I would probably just not go - sounds absolutely miserable for you anyway, and your children are going to be in nursery all month anyway so what is the point?

And if your FIL doesn’t like it, tough honestly. What is your DH going to do, divorce you?

I just wouldn't go over there unless its for a holiday and you have eyes on dc the whole time.

You stay at home with dc. Let dh go.

Problem with this is she then can't stop him letting his parents babysit her kids during his contact time.
I could never have sex with such a wet blanket though.

Sorry they would never see my dc who at 1 could not tell me what is happening.
so he assaults your dc and injures them, what do you tell police, ss, hospital.. “yeah we know he’s a child abusing bastard but…..”
why doesn’t your dh work?

Are you going to visit them? I'd refuse to go if DH couldn't assure me he'd protect our children.

In laws hit their kids and grandkids. They say their kids used to ask them to discipline their kids for them. I said I don't need anyone to discipline my kids for me, I'm their mother.

They are not allowed unsupervised around my children, ever. DH knows this and supports me in this. He is scared of his parents. They are majorly abusive to him. But I don't take any shit and he knows that respecting me and protecting our children is more important than his parents tantrums so he has the hard conversations.

I would tell them they're not to hit your children. I would also change my working hours to do he collections. And if anyone asks or complains I'd say "i can't trust you not to hit my kids and I can't trust my husband to protect my kids so I have to do the school runs aswell as work" let them all be embarrassed, they should be.

Why's your kid in daycare when your husband doesn't work?

Honestly eiither you change your work hours & do the pick ups or you & kids just don't go
You have a DH problem.

This would be enough for me to rethink my relationship altogether. Even if he doesn’t hit your child, you do t know what else he might resort to and unfortunately, everyone, including your husband, permits this. You have to protect your child.

This is mainly about your FIL’s need for power and control, there is absolutely no value to hitting children. Is your DH playing the same game now with you? His need for control and/or power is more important than your children’s well-being.

Absolutely not! I found out that PIL used physical abuse to discipline DH and his siblings. I made it very clear before DC1 was born that that would never ever be acceptable and if they laid a finger on our children, I would cut their contact with them. He agreed!