Maybe you could swap the kitchen and living room. Then you would have more space for the dining table, and the staircase could serve as a "room divider." What have you planned for the kitchen? Kitchen island, counter?
I don’t think the staircase solution itself is bad at all. I like it when you bring the groceries straight into the kitchen, so you don’t have to carry them very far. What could eventually become a problem, however, is the open dining area upstairs. That could eventually disturb the children when they’re sleeping or, conversely, disturb the parents when the children are listening to music. As nice as a gallery is, unfortunately, it also has some disadvantages. And one more thing: if possible, always plan doors with a distance of 65 cm from the wall. That way, no space for furniture is lost. Do the children’s rooms only get such a small window? That will be quite dark then.