Just in case you haven't seen it, here is a link to a short article on spawning.
http://www.vcnet.com/koi_net/spawn.html I would take Steve's sugestions on getting the food supply ready for the fry. I tried the Liquidfry and live brine shrimp route myself last year with limited success. Per the article, using the willow branches to receive the eggs seems like a good suggestion. My koi spawn very easily in May if I keep them cold all winter and then move them into fresh water like the article suggests. To me getting the fish I want to spawn together, when I want them to, has been easy. Raising a bunch of them without stunting is more of a challenge IME. Good luck.
Mitch