Floor plan for a single-family house with 4-5 children's rooms

I would omit the dressing room. They take up a lot of space. Instead, plan a long wall for the wardrobe. And built-in closets in the hallway/bath area. 45 sqm living area is too small for 6-7 people.

Giving up the family bed is not an option. The new building should bring an improvement in quality of life. That is indeed an absolute must. Nothing is more important than a good night's sleep…

We currently have just under 45 sqm of open space and don’t find that too small. At the moment, most family members are still there at the same time. That will probably decrease with age. We already have a huge dining table, a couch that is probably bigger than most others, and a very well-equipped kitchen with enormous storage space. There is actually nothing I need to improve there. It would be nice to have an adjoining playroom right now, but that won’t be used forever, so it’s not necessary.

I definitely forgot the pantry!!! That must not be missing.
We currently have a lot of dressers etc. and have actually used the storage space quite well. But the utility room can be bigger or an additional storage room would be nice.
Yes, we have certainly accumulated a lot as well. That is definitely true!

In our basement, we have tools, beverage crates, a laundry room, technical equipment, and a storage room for all sorts of things. Some of it would go into the storage room, some into the utility room, and sorting out would also be nice.

The currently unused children’s clothes are in a small mini room in the attic. Without an attic, that is probably not possible.

That sounds more like you should consider an extension of your house. What you want will cost you (only for the house) around 600,000 euros.

We now have offers from two providers (Viebrockhaus and Hanse Haus), which still need to be revised but initially leave enough room in the budget.

And we have found an architect who also has a large family. He also says that it fits.
We will wait and see.
When all three options are realistically planned, I will present them.
I am also not familiar with the topic of "solid house" vs "prefabricated house."
And I also have to carefully review the construction and service specifications first.

But thanks for the tip. That is definitely an option, and especially with this decision, we also need help. Everything has its pros and cons.
Adding on is also a stressful task. A few extra euros plus a new heating system for us would also need to be planned.

Giving up the family bed is not an option. The new build is supposed to bring an increase in quality of life. That is truly an absolute must. Nothing is more important than a good sleep …

Then later you would have a bedroom that is way too big.

How about combining your bedroom and a future children's room. It could initially have two doors, two connections for controlled residential ventilation, and later a drywall partition can simply be used to separate a children's room. It’s a matter of two days... and meanwhile, you would have a bedroom that is big enough. The two youngest could initially still share a room for the time being.

I definitely forgot the pantry!!! That must not be missing.

Then include it in the room planning as well!

The currently unused children's clothing is in a small mini room in the attic. Without an attic, that is probably not possible.

When finishing the attic, please don’t forget the escape route and build a proper staircase up there right away.

That's a good idea! Sharing a room is no problem! That way we would make good use of the large bedroom. And the sensible staircase to the attic, for example, is something that has been really poorly planned here recently. Ours is totally steep and actually dangerous. Although you only use it in the morning and evening, still... It should be better! Yes, an escape route must be planned. We know that from the current attic conversion.