This bay window is insanely expensive and doesn't bring much. Draw the furniture to scale in all the rooms once. Especially in the bathroom and take the rough construction measurement of the shower. Move the door in the smaller children's room so that a wardrobe still fits behind it. The garden access is missing in the basement. The advantage of the slope is that you can always get out everywhere.
You say nothing about the age of the children. You have a relatively small terrace for eating upstairs. Garden access downstairs. For me, an absolute no-go. Should the children have to go up and down the spiral staircase every time to get themselves a drink? Do you want to walk that distance for every glass of wine? I would remove the bay window, build a large terrace in front of the ground floor, possibly push the basement forward, and use the cellar better. It is there and it is paid for.
Try to make the lower part of the garden accessible for wheelbarrows, sack trucks, and the like. The stairs are not great for carrying. Whether flower pots, lawnmower, the sack of mulch, grass clippings, or swing, it has to go from top to bottom. Plan the outdoor area as well. The excavator is coming in now, later it will be more difficult.