I really liked the idea so I tested it on my children and they loved it. Here are some suggestions.

I draw mode
1. If I klick on the pencil I would like to have the pencil. not a choice. Put another icon for marker.
2. I would like to be able to always have a window for a/ pencil/marker/line thickness
b/ fast choosing of colour. let say 10 standard
Almost as you have in text mode
3. It would be nice if I could get a "stamp" with some standard figures and to be able to set size.
4. I really would like to be able change size of window and be able to "maximise" the "window"
5. be able to see the "side" of the paper. As if it was a real paper you was drawing on.
6. Move Color and New icons the the bottom. Where undo is. (in text mode)
7. Be able to change font color.
8. See the text when you "klick" it in

I text mode
1. Be able to set/change the size of drawing and let text flow around it.
2. Be able to mail it without saving it first.
3. Be able to see the "side" of the paper. As if it was a real paper you was writing on.