Rough estimate of construction costs for 220 sqm

So it's possible, we have 150 sqm of living space without a basement. Our bedroom is 17 sqm, the two children's rooms 13 sqm, office 9 sqm, then a bathroom (not two) and a spacious hallway with floor-to-ceiling windows. If you go to 200 sqm, you have 100 sqm per floor, with 25 sqm more that's almost like having the 4th room included. And also remember that less space not only means a smaller foundation but also fewer windows, fewer sockets, wiring, and tiles... that adds up.

and a dressing room? We have so many clothes that we definitely cannot fit them all in a wardrobe. Then the dressing/guest room is still missing. When visitors are here, they should not have to sleep on the couch.

If it is not feasible, then it is what it is. Then I have to admit that and move into a rental. Although for renting I would also have at least 1500 EUR cold per month.

Dressing room? I have a 17sqm large bedroom and my almost 4m long wardrobe fits in there along with a dresser. Winter clothes can be stored in the attic. My guests don’t need a dressing room; they are welcome to sleep on the couch in the office room, it doesn’t happen every week that someone stays overnight. And why shouldn’t the guests sleep on the couch? Do you want to put an extra double bed for them? I think that’s pointless, unless you really get visitors every month. And honestly, if I visit someone, I have no problem sleeping on the couch and don’t expect a bed and room just for myself. You can set up a 12sqm office/guest room on the ground floor, that’s more than enough. Upstairs you can even add 2 bathrooms. Think carefully about this, with 3 kids there’s a lot to do, whether you want to clean an additional 220sqm of living space is questionable. If you have that much money, you can plan it the way you want. But you should have some connection to reality, because none of this is free.

of course. The guest room on the ground floor is used as a dressing room, for example for winter clothes. A pull-out sofa is planned in there. So I would say it's not luxury or anything.

yeah no it's not clear, above you still write: When guests are there, they shouldn't have to sleep on the couch. And now the guests are supposed to sleep on the couch after all. If the guest room is to be on the ground floor, then 90 sqm upstairs are more than enough for 3 children's rooms, one bedroom, a bathroom, and a hallway? Get some quotes first and if you can afford it, then there's nothing against planning a walk-in closet for each child as well.

it is only meant that the guests do not have to sleep on the couch in the living room....

Here in the area, a house with 340 sqm of living space is offered for 360,000 EUR, built in 1996, without a garden.