I just wanted to say "Thanks!" for all the great comments. These will probably work pretty well for younger kids who have a tendency to kick off the blankets at night. They may be a little too thick for older kidlets though.
I didn't really notice until I started sewing that it wasn't the same as regular flannel. It's not horribly thick, but there is a noticeable difference.
My oldest two want me to make them housecoats out of their old blankets... I'm not too sure how well thats going to turn out