In the initial consultation, it was only said "they wouldn't plan it that way"
Of course they wouldn't do it that way, because they don't have a design for that in the drawer and would have to think about it.
I would never plan it that way with small children.
Valid point - therefore plan the access to the garden from the living level and anticipate the coexistence. How much and what do you want to get done when the little ones are in the garden? How anxious are the children and the parents?
You have no access from your living area to the garden.
That is a question of creativity and budget and has a huge range from balcony-with-stairs solution to ramp to partial backfilling against the house with and without slide... You have to see the terrain to get creative.
If I think about frequently using the view and the balcony/roof terrace from the living area on the upper floor, I’d rather buy an apartment.
Alternatively, you could also think of the garden three-dimensionally. How can you access our garden at ground level from every room in the house (except the bathrooms of the children's apartments), whether basement room, living level, or upper floor level. It is a question of the terrain.