Single-family house - "almost" final floor plan - improvement suggestions???

We definitely don’t want another bathroom. We both grew up in basically similarly structured parental homes and find it perfectly fine that way. Besides, I’ll have a total of 3 bathrooms later on when the kids have moved out

Just my opinion on that again, of course, in the end you have to decide how you want to handle it...

Your kids will basically shower every day, how often do you actually have overnight guests who will use the bathroom on the ground floor to shower?

Your kids won’t tidy up the bathroom every day, won’t squeegee the shower every time, might leave the sink dirty.
I wouldn’t want that in my guest toilet/bathroom (assuming they “take over” the lower bathroom, which I assume with 4 people potentially getting ready at the same time).

Guests always have their change of clothes and toiletry bag with them when they go to the bathroom at your place, so it doesn’t matter if they carry it to the first floor instead of through the hallway, but with your own children, you actually want to offer more than having to run through the house half naked every time they forgot their fresh underwear in their room.

And yes, you then have a third toilet in the house, but I really wouldn’t find that dramatic, since the shower downstairs would then be omitted.

To quote a father of three with a children's bathroom: "If you like cleaning and have too much money left over, build a children's bathroom." The day has 24 hours, and in 2019 it should be possible to coordinate who showers when.

We often have the kids' bathroom yes/no discussion here. I myself am glad that we have one, even if at the moment it is not the kids' bathroom but the dad's bathroom. But I also think that with a house size >200m2, certain things are more of a standard than with the Flair 113. And quite honestly, with a project of this size, an extra square meter for another shower doesn't really matter... In the current floor plan, anyone who wants to go to the toilet from the bedroom has to walk through the entire bathroom each time to lock the door to the hallway. And then back again. Maybe not now when the kids are small, but once they are teenagers and still have visitors at night, a trip to the toilet can definitely overlap.

To quote a father of three with a children's bathroom: "If you like cleaning and have too much money left over, build a children's bathroom." The day has 24 hours, and even in 2019 it should be possible to coordinate who showers when.

Well, I don't clean the children's bathroom, but my children are already grown up. However, it wouldn't work for us for our son to shower on the ground floor because the stairs would be soaking wet afterward, the entire shower room on the ground floor would constantly be messy with wet floors, perfume smells, and clothes scattered on the floor. But there are surely children for whom it might be different; for us, the children's bathroom is very important.

Best regards Sabine

In the current floor plan, anyone who wants to go from the bedroom to the toilet has to walk through the entire bathroom each time to lock the door to the hallway.

Why should anyone do that – because of the monsters from Minecraft? Anyone who would react hysterically to their own naked parents/children/siblings can simply knock first. After all, no one watches Alfred Hitchcock immediately before every shower.

well, I don't clean the kids' bathroom,

I would also advise against that for pedagogical reasons. The kids' bathroom is a good learning station for personal responsibility. If mom cleans it, the boy will still be living in the kids’ room at 42.

You could also simply provide bathroom connections in the storage room between the children's rooms. If the shared bathroom becomes annoying, a bathroom can be realized here without much effort. And for a possible resale, it would also not be a bad idea. On the topic of a small air space: we have about 3x2.2 m of air space and the effect is really great. We solved the noise problem with an all-glass panel on the upper floor.