Janet, I know that your granddaughter does not fall into that category, but I'll tell you anyway......
I work with special needs children (11 to 16), and a lot of them are a lot younger than their actual age. I find the following most important:
- Constant (but discreet) supervision. Most common reason for stopping them and 'interfering' with their sewing: They have managed to get the thread all muddles up, the machine makes a terrible noice and stops sewing, but the kid continues to step on the foot petal. 'Wonderwoman' here then has to clear all the thread out and rethread the machine.
- Some youngers find it difficult to coordinate feet and hands, and a machine that can be stopped and started by button helps a lot.
- Most importantly: A machine where the speed can be de- and increased. To start with, a slower maximum speed helps a lot. This can then be increased as the child gets more confident.
- If you start a youngster on a 'kiddy-machine' they'll outgrow that machine very quickly. I would recommend a normal sewing machine, but not a large one that looks intimidating and has too many functions. I'm using Janome Jems very successfully with the kids in school. Another excellent starting machine (if you can find one second-hand) is the old Frister & Rossman Cub4. It takes a lot of abuse and continues working.
- You should also consider that your granddaughter may actually like to use the same machine as Grandma does. I know a quilter here in the UK whose 9-year-old grandson sews on Grandma's Bernina 830.
And above all: Have fun!