I find the floor plan nice and simple.
Did I overlook it or what are the cardinal directions on the plan? I assume south is at the bottom, then I don't like the room arrangement on the upper floor. For me, children's rooms should always be on the south side because they also spend time there during the day. A closet would fit better in the north.
I find the entrance area very large. Pleasant and nice, but also costly. Open under the stairs?
No basement? On the ground floor I would miss storage space (vacuum cleaner, broom, drink crates, tools, ironing board, ...)
I find the living/dining room very elongated, definitely try furnishing!
Is the heating going to fit in this small area? A friend also has geothermal heat and in her 3.5 m² technical room it is extremely tight (many pipes!). Compared to the size of the WC, that doesn't seem okay to me for your plan.
Is there a shower option on the ground floor? I would at least pre-plan a connection in case it becomes necessary.
In my own plan, I like to have technical room, utility room, kitchen, bathrooms, etc., as close to each other as possible. Not only to save on piping but also so I don't have to wait so long for hot water.
I would also consider whether you want a separate WC on the upper floor. We are considering whether to have a separate children's bathroom.
Have fun planning!