I bet one of the princes suggested random children. No sculpture would use their initiative to come up with such a bold departure from convention.
It seems like an initial idea, with a bit more tacked on, and then an afterthought added, and some element discarded. The finished article looks like the product of some difference of opinion, and a compromise solution. The outfit could be seen as part way between very formal state occasion evening wear and casual wear.
Good sculptures usually have a feeling of unity: religious statutes with the energy flowing out from the outstretched hands and perfect stillness of the body. Poise is everything. The ideas in this work are a bit juxtapositioned and messy. Diana would definitely have leaned in to feel the presence of any child she were with. It is like somebody has said: " Oh no, but that's too informal", and here we have the in-between stance, rather like an air hostess shepherding the kids up the stairs to the plane, but remembering to maintain her upright professional posture, at all costs.
But it's hard, because she was quite informal when she ceased to be married to Charles, and yet a princess and jewel in the royal crown, when she was with him. So which person do you capture?