Maggie, here's a idea to share.
Check out the gallery at
www.pta.org/parentinvolvement/reflections02/index.asp
and then print some of the winning entries of last year - so the kids can see that the work isn't that of necessarily an outstanding artist, but instead of the work of a child - a child that was able to put their feeling onto a poster, or see something cool through a camera etc.
After your print some from the gallery, put them on posters and hang them up in the cafeteria for kids to view the gallery. They don't lool the work up on the internet, but if you do that for them, and they see it ove and over, (maybe you could have a table set up for them to come up and ask you some questions - like who did that, how old was that kids - is he an artist or just a kid ---- you get the point), maybe you'll get lots more entries.
If you have the display out in the front foyer too, parents can ask questions when they come pick up their kids.
Sometimes we just have to think outside the box. We just can't send home a form and expect parents to just take to the idea - it goes on a pile of paperwork to look through some day. You can help them realize that their child can submit something, and maybe it will just be the winning enry!
Keep practicing that word NO but not in front of the students since they need to learn - YES - I Can Do That!