House or car special repayment at the end of the year

Depends on whether you need the liquidity you get from paying off the vehicle early or not.

It's like with people who split their home loan into several tranches. Some pay off 1 of the 3 loans early with a special repayment and then enjoy higher liquidity after 10 years, while others stubbornly pay the same rate for 25 years despite special repayments.

All in all, it brings more flexibility

Stroller = €1,000 spent just like that
Children's room = €5,000 gone just as quickly
Child seat, high chair, clothes, toys, etc. are not cheap either
Childcare if desired = several hundred € per month

What does a stroller that costs €1,000 do? Does it take me and the child to do the shopping by itself?

We had a stroller for €70 and a buggy from the flea market for €5, which was enough for 2 children.
But yes, furniture can cost quite a bit if you buy something nice made of solid wood.

What does a stroller that costs 1000€ do?

It has an integrated espresso machine. But seriously, fancy new ones often cost significantly more with accessories. See Bugaboo and others. From the third one on, you get used to it.

How would you decide?

I would decide based on my gut feeling.

Otherwise:
If the amount for the special repayment comes from a constant surplus --> special repayment into the house, because liquidity is then not a particular issue and economically this is the better leverage.
If the amount for the special repayment comes from a one-time grant and the monthly burden is pressing --> put the special repayment into the car.

Comes with an integrated espresso machine. But seriously, new fancy ones often cost significantly more with accessories as well. See Bugaboo, among others.
From the third one on, you get used to it.

You can easily spend that much, but you don't have to. It's more of a brand thing. The costs for children can vary greatly depending on whether you already inherit a lot from the family. The clothes don’t all have to be new.
Things that aren’t strictly necessary but that you still want, like bike trailers, also cost money.

.
But yes, furniture can be quite expensive if you buy something nice made of solid wood.

Everything complete, 70€ eBay classifieds. 13 years old. but hey, solid wood. I don't worry about that.

The expensive ABC (Viper) can do everything the others can, it just doesn’t say Hartan on it. Also costs only half as much.

As long as the grandmas are still alive and liquid, you actually don't have to buy anything yourself.