Without meaning to accuse you of anything, I have the feeling that you are quite resistant to advice. Several people have already repeatedly criticized the same thing, so think about whether there might be some truth to it.
What hasn't been said yet: I find an estimated 9.30m interior width for cooking/eating/living quite narrow. What exactly are the windows there? How and where are the doors supposed to be to the outside? Where will the terrace be?
You can tell that you are not yet prepared for children and that you still view life with children through rose-colored glasses. Children are not always tidy, children bring friends home, children don’t only play in the garden (there is also bad weather), children are not quiet, children will eventually not want to play in the living room with mom and dad anymore, mom and dad will eventually want a toy-free living room again, children don’t have just 2 pairs of shoes and 2 jackets, children run inside the house too, not just in the garden, .....
You already have a relatively large utility room compared to others. But with children it will still not be big enough. With children, you will wish that your utility room has access to the outside—especially in winter and when it’s raining. You will hate the stroller—at your place it will certainly stand in the study (great with wet wheels, having to go through the whole hallway and the living room), because there is no space for it in the utility room and the hall, and the garage is too inconvenient.
You don’t have to throw the whole concept overboard. I actually find the layout fundamentally very successful. But there are small details that still need to be ironed out. Straighten this stupid setback at the entrance with the master bathroom and you will gain about 6 valuable square meters without changing the bungalow’s appearance much.
Regarding the attic stairs: as the floor plan is now, you will only be able to fit a pull-out staircase there.
In the hallway, I still don’t see any possibility for a wardrobe. I would omit the door between the children’s hall and the entrance area. That only adds to the narrowness. These two wall stubs when you come from the hallway into the living room—I would make one wider (sensibly the left one) so that you can put a wardrobe against the wall before it, and I would completely omit the other one.
What else comes to mind: maybe consider whether it might make sense to put the office entrance on the side of the children’s hall (in case a third child should come or it is to become a playroom) or at least plan a door lintel in advance as an alternative, so it can be changed if necessary.