My nephews designed their own quilts on paper. The youngest about 5 at time watched older brother draw a layout etc of what he wanted. After along time of silence when I was wondering what he was up to. He produced a piece of paper with 5 year old squares and inside he had tried to draw dinosaurs. Brother was very much colours in a specific order , little one wasn't bothered about colours just dinosaurs in squares.
I did most of the sewing at home but they both helped to sandwich and did do some quilting. 2 boys one machine and only a few hours did mean sharing. Ask the children to design their own .if they are at school they will know what to do.