Wein's slaves now work with digital pre-flash, but you need to be careful about which model.
IMO optical slaves are secondary options for modern systems. My Skyport fires two Vivitar HD285 (cables from
www.flashzebra.com are necessary)...they can be located places/distances where optical slaves wouldn't work. I also have a 25-yr-old Wein peanut slave mounted on an equally ancient Sunpak strobe, which works fine as a third light (eg behind a subject)...actually better than Pentax or Vivitar (just as powerful) for that purpose because of the way the head swivels.
You'll go wireless as soon as you understand how well it works. The systems on 'bay may not be 100% reliable but they're very cheap. I spent more and got Elincrom Skyports. AlienBee has something similar, but I prefer Skyport's far-lower on-camera profile.
For more about wireless and off-camera flash:
Strobist ...which incidentally sells a SUPERB set of DVDs that teach off-camera lighting from soup to nuts :-) I think you can find all that DVD info somewhere on the site, but it's faster and more visually effective from the DVDs.
...as for red-eye and optical slave: no red eye if you aim the flash UP and perhaps gobo (baffle) it so it doesn't fire directly at the subject, the bounced and bouncing light will fire the slave IF it's not positioned too far away. "Too far" depends on all of the elements, including ceiling height.
It MAY be possible to gobo k10D's built-in flash to do this...or may not be.