There was an interesting post somewhere out there in the blogosphere recently (sorry, I can't think where! ;) about colouring-in. And the benefits of not. Well I do agree to a point but Hug actually really likes to colour-in. So, in turn, I think it's important to make sure he has good-quality options & one of my favourite choices (and his :) is colouring Mandalas!
There is something so beautiful about them & the inherent patterning and symmetry. When I've done one myself I'd even say they have a meditative quality. I have bought one book of Mandalas but mostly I like to do a quick google search & I'll always find a few free ones to print off, like these: Mandali.com, JuneMoon Free Colouring Book.
Please let me know if you have any links to suggest!
p.s. Looking for links for this post I found this book of Peace Mandalas for children which I can only imagine would be wonderful.