If eyelets would look ok, then would brads work? They have a similiar look about them but are really easy to use. Just put a very small slit in your page (both the K&Co and the CM page), and then slide them through and open up the back.
Hmm - just had one thought, which would be a problem with eyelets too - what is on the back of your CM page, because both the eyelets and the brads would be visible on the back of the page.
if you use photo squares, they would be on the back of the page, so I don't see why they would be visible if it's not vellum.
I have found the hermafix tabs to be very good.
Bev