Alexandra has always been on the floor. She is twelve and very petite, size 7 and as you know she do not stand or walk. But she sit very well and have great strength in her head neck and back. I like this position especially with the hands distributed on both knees.
Being on her belly has always been hard for her, she is getting better had it. The ABM therapy has helped the curve of her back, because her 45 degrees scoliosis made it a little bit stiff. http://www.anatbanielmethod.com/children
This pose is ok too, I still like the arms moving around toward the back body and front. Very important that she experiences a wide ranges of movements.
Encourage your child movements, and observe the small movements she is doing. Praise her gently and move on.
Alexandra can stand on her knees, this is very good for her hips sockets, weight bearing and overall movement.