Hello to the Upper Palatinate,
I made two attempts to change the house so that the basic structure remains and only the two children's rooms become larger.
In this variant, the north wall at the corner is pushed to the building boundary and children's room II on the upper floor is cantilevered over the covered entrance area. This results in children's rooms with approx. 15m2 and 18m2. Additionally, the dressing room and the bedroom become slightly larger, and the staircase can be moved a bit to the north to make the area in front of the kitchen more spacious.
Variant 2 has a (not unusual in the original Bauhaus style) curved wall on the ground floor and enlarges the children's rooms on the upper floor up to the building boundary as well as the roofing. Otherwise, all walls are the same. In principle, I would give the children's rooms windows in 2 directions. In my opinion, this simply creates a much nicer spatial impression.
If you go all the way back to the placement on the plot, you should be allowed to build ancillary structures (carport, shed) outside the building window? This would be helpful for placing the garage in the north or northwest. Although I can quite understand the architect's idea of using the carports as a privacy screen from the street to the private garden and pool.
Your price estimate also seems rather tight to me. The house is architecturally rather extravagant. If you want to be similarly elaborate in the fittings, the 550k will probably be very tight.