Live over 225 miles away from family

I think if you can afford it then it's a great idea. Go back to hotel and have a good night's sleep. If your husband's recovering from surgery he might be glad of disappearing to have a bit of quiet time.

I would be disappointed it's very thoughtess of them but still go and help out if you can afford it. However I would consider it a one off.

You need to think about whether you are available for this at all. If your husband is recovering, is he up to that drive? It seems pretty rude to ask this of you and not allow you to stay with them for the short time needed. It's up to you if you can and want to do this but you don't have to. Just give them plenty of notice if you can't, so they can make other arrangements. You can also make your help conditional on being given a place to stay for a couple of nights. "I want your help and these are the terms of giving it" doesn't sit right with me. It seems like there should be room for accommodating you while you do them the favour.

Is the birth a planned C-section? Otherwise how do you know when to book the hotel? Will they phone the minute she goes into labour, which might only last for a very few hours with a second baby, so what guarantee is there you'll get there in time, or that a nearby hotel will have a room available? If they'd rather you didn't stay in their spare room they should at the very least pick up the hotel bill themselves. I think they're being very cheeky!

Families ! I would offer to have him down where you live or not at all. They could drop him off to you, not that far when you are young ( certainly not by my standards over here !)

When our first DGC was due, I wanted to go to be nearby soon after the birth and booked an Airbnb.
Like yours, DS and DDiL live a long drive away.

In the end, she was born by emergency C section so DiL stayed several days in hospital and DH and I stayed in their house with our DS.

I wouldn't have wanted my or DHs parents staying at that intense time. So I don't actually think your family are being unreasonable A SHANTY - it's a privilege to be asked to help them out.

Can you travel by train to save driving?

When our first DGS was born, 2 hours drive away, DH and I, also the maternal Grandma, who had travelled from the USA, stayed in a nearby b&b. We spent time with son and family but didn't crowd them. They needed time to be on their own with the baby.

Thank you for all the advice.
I know it’s a privilege to be asked as they have no other friends or family living nearby, so would struggle otherwise.
We’ve been asked to go there about one week before due date (no planned c section) I’ve already mentioned baby may arrive early/late. One of our worries is how long to book accommodation for as we’ve no idea. It may be that we book one place, but need to find somewhere else too if we’re needed sooner or can’t extend our booking if we’re needed longer.
If my husband isn’t up to the drive etc., I’ll have to go by myself.
We need to travel by car as we’ll need access to transport.

"You have been told to find and pay for accommodation". For an unknown time too. Seriously?
And your husband is expected to sit in a car for 5 hours after a hip replacement. He would need to break the long journey and stretch his legs a few times.
They have a spare room. You need to talk to your son and remind him his Dad has had a hip replacement. Much more practical to stay with them so you can look after your husband and the toddler without the financial stress of a hotel. Otherwise surely your son should foot the bill. He's expecting free childcare after all.
You could go alone but do you want to leave your husband alone?
Or your son could bring your grandson to your house as suggested above.
If I were you I would have a converstion with your son and explain things from your end.