My oldest daughter was so excited to start her first sewing project with a "real" needle. It was just about this time last year. She made a Mother's Day card for Grandma Mary.
She started with a piece of felt and drawing a simple picture with a disappearing ink fabric pen. She was ready to go.

Here is the finished embroidery project after it was attached to a card.

Be patient with kids who are learning to embroider. It may involve a lot of helping remove stitches, making knots, and finding the needle when it's dropped...on the carpet!
Here are some kid's embroidery projects I found at Flickr:

1.
Kid Embroidery, 2.
First Embroidery Project, 3.
Embroidery Samplers, 4.
more embroidery