To think DH is insane to suggest this

If your family are coming at Christmas then you wouldn't be alone Op but would they be upset if your DP takes your DC out?
I'd keep in mind that if his EX doesn't meet anyone else she may want her DC every year and this could be an ongoing problem, so the solution has to be one you and your,DP are both comfortable with.

I agree with this. You sound like you don't think it's a big deal for him not to see all his children on christmas day. You see the two children he has with his ex wife and the one he has with you as separate but to him they are just all his children.

Move your Xmas day to Xmas Eve.
Then for SDC they go to their mums for Xmas day but it's effectively Boxing Day for them.

No, it's clearly his ex who is in charge

You’d “have him”? Are you in charge?

There's nothing wrong with him popping to see them for a few hours in the afternoon. It will give you a few hours to decompress after a hectic day. Not sure why he needs to take your the youngest, but if she'd enjoy seeing her siblings I would allow it. If she's not bothered keep her home with you and go for a nice walk or something while he's out.

However I think I the main issue here is his ex thinking she can just change the rules based on her own wants and circumstances. It isn't your problem that she's broken up with her partner and presumably if she hadn't then you wouldn't be having all this change of plan. Your dh really needs to be standing up to her instead of pissing you off on Christmas Day.

No don't let your three-year-old go to his ex-wife's house for the afternoon. There's no way I would let that happen. I wouldn't have your husband go there either. I'd have him go and pick up the kids and bring them back for tea and take them back after two or three hours. If she's got them in the morning afternoon and later in the evening then that's fine.

It's also not thoughtful to propose taking a 3 yo - prime 'magic of Christmas' age - off for part of the day to what is, to them, some random's house. Ex is not her step mum, and I can't imagine she'd rather be with her teenage siblings - who she'll see the next day anyway - and dad, over her mum, grandparents and her new toys to play with in her own home. That's just a selfish bit of this plan from the husband and I'd have none of it

Sounds like my ex husband. Didn’t give a shit about our children together.

Yes it’s unfair to change the agreement, and he needs to grow a backbone and stand up to her, not changing the usual plans for one person. She can go visit one of her family members/friends while the DC are at yours surely? Does he always give in to her demands? Unfortunately these scenarios often come with blended families.

The set up of a shared day was bound to fail at some point. Better to have just done alternate years.

Anyway, this is a man who loves his children and whilst his suggestions aren't great foe you it looks like he's clutching at straws at trying to see his children on Christmas Day.

My suggestion would be, why can't he go and spend a morning at his ex's house to see his children and then come back home for the rest of the day.

That way he sees you and your child first thing to open presents with your child and then he sees his other children.

Put your foot down and tell him that your DD will be going nowhere on Christmas Day. How unsettling for her anyway to go to a strangers house on Christmas Day. She will want to be at home home playing with her new toys etc anyway. It’s a ridiculous idea. I would be fuming.

onion88, you can't project your state of mind onto someone else.Be the bigger person here and let husband and child pop round. Get pissed on Buck's Fizz and you won't care. Make sure she doesn't make any more demands though and make your husband be aware of this. You will only get more stressed and hurt and Xmas will be ruined for you. Your husband will think you're wonderful. You can let rip after Xmas if you're still feeling resentful.x

That would be the case with the normal arrangement too.

Honestly I couldn’t be bothered with the utter drama of step/blended families it just sounds so awkward and unpleasant for all concerned.

Not really, as with this solution the ex isn't without her children at all on Christmas Day, whereas OP is because her child gets taken out for the afternoon away from their new presents. It's a worse deal for OP and the youngest child.

Tell him he can go but the youngest stays with you. Can't see her wanting to go or her siblings being bothered - they'll see her the next day. Agree with making Boxing Day the big event with them. It might be better to move away from the swapping on Christmas Day itself anyway as you say.

The day is normally split anyway, and this year the ex would have them in the morning and him in the afternoon. Because she's now single she wants them ALL day and changed the rules.

his lack of apparent spine would drive me bonkers to be fair.

Why do people think it's reasonable for the OP to be separated from her child for a few hours so that the ex doesn't have to be separated from hers?

I'd have no problem with him popping around, but not with the little one. How would he feel about picking them up around 6 p.m. on Christmas Day, if allowed, sleeping over, and then having another Christmas Day on Boxing Day?

I can see his upset and I can absolutely understand yours too.

I can totally see your point - its not even that you might not be ok for a few hours alone - its the principle that in his eyes ex comes first and your feelings second.
It would be perfectly acceptable to suggest I want the kids for a few hours in the afternoon even if its not Xmas Dinner but I'm with you - the arrangements have always been a split Xmas day - can't see ex offering up the kids all day if you and dh split next year! This is a DH problem and he needs to see that if he puts ex first then it will probably be his last Xmas married to you.

If your DD and her siblings get on I think his suggestion he takes her to see them for an hour or so is a reasonable compromise.
I'd quite like an hour on my own on Christmas Day, put my feet up and watch what I want for a change.

I would love a couple of hours to myself on Christmas Day!