We also built a bungalow. Experiences with 2 small children:
Keep the utility room away from the children's rooms. The heater kicking on or the washing machine spinning wakes the little ones up and you as well.
The children can look from their rooms into the living room. That wasn’t intentional, but it led to both of them playing in their rooms very early on. Definitely not a must, but quite practical in the first years.
The bathroom next to the children's rooms apparently doesn’t bother them at all. Neither the baby nor the 5-year-old is disturbed by the flush. Loud singing in the shower should still be avoided.
Leave out the stairs upstairs at first. You are young and can just use the classic hatch. If you really need stairs up when you are older, you simply tear down the walls of a children's room (which is easy in a bungalow) and put stairs there. Saves you money and space now. With stairs leading to the attic, you either need a specially sealing door or you must definitely finish the attic. Our neighbors didn’t know this and after a year there was mold upstairs. But having the attic as a buffer provides pleasant temperatures in the house in summer. The neighbors liked to sit with us in high summer because they were roasting in their huts and we had a pleasant 24 degrees Celsius.
Then make sure to have good shading, that’s worth its weight in gold, and you can choose somewhat larger windows so enough light comes in.
See if you can get a double door with glazing facing the living room. Especially in a bungalow, this brings pleasant light into the hallway.
Leave out the door to the living area. It only makes the hallway unnecessarily dark and will always be open anyway. We originally had this in our plans and it’s somehow nonsense.
My suggestion: leave out the stairs, basically rotate the bathroom, and thereby create a wider hallway in the living area. This creates a more open living concept and feels much nicer overall.