Giant Floor Drawing
Tape a huge sheet of paper to the floor and let them draw on their hands and knees.
A bucket of water, a decorating brush, and a whole wall to paint.
Zero mess, zero cost, and toddlers will do it for forty minutes. It evaporates, so they can start again.
Large brush strokes on a vertical surface build shoulder and arm strength, which is the foundation that later fine-motor control sits on top of. The fact that it vanishes removes any pressure to make something good.
Supervise around buckets of water. Empty it as soon as you finish.
It cleans itself.
Tape a huge sheet of paper to the floor and let them draw on their hands and knees.
Start with one scarf. Most people never get past two, and that is fine.
You describe. They draw. Nobody looks.
One window, one pencil, twenty minutes of genuine quiet.
Coloured water in a spray bottle and a garden full of blank canvas.
A tray of rice, some cups, and twenty minutes of total absorption.