My Toddler at 18 months of age using large wooden spools on a shoelace. He is at the very beginning of his sewing journey.
My 3 year old:
Bead sequencing, beads on pipe cleaners (copy the pattern)
Pony beads on acrylic wool.
Small beads that vary in shape on stretchy elastic strands.
Wooden beads on coloured string.
Sewing on hessian material.
My 3 year old using these lacing cards we were given as a gift. They come in a pack and vary in difficulty.
Paper weaving on a weaving frame.
I am only slowing going though this book, but there is lots of great sewing ideas in it.