I use a 100-page, 60 lb. drawing paper sketchbook for my year-long kids.
Next year I will get them to apply clear shipping tape on either side of
the spirals (this will be tricky) to keep the covers on. I agree with
Randy re: quality of paper and bidding.
I think I'll also have the kids create a pocket on cover page three (inside
back cover) for notes. And I'll ask them to use the back 20 pages or so
for their own (non-related to art class work) sketches.