Since you dislike small rooms and your wish list includes a spacious kitchen, a guest suite, large closet in girls' bedrooms, a large office for 4 people with toilet and you receive clients in the office, the garage should be able to take 4+ cars, seating capacity for cinema is 6..
Then you said that the total area - bottom and second storey including the shed - can be a little bit flexible..
So, I came up with this proposal which in my opinion, the size for each room is much more suitable for comfort.
Total area = 671 m2 (including shed):
1st floor = 423 m2 ( including laundry+ media room in the shed)
2 nd floor = 248 m2 ( including office in the shed | loft room)
This simple elegant modern house has a timeless concept, using natural materials and lots of glass to views.