To the OP - I don't know how early or late your dinner reservations are, but
@CaptainAmerica has a potentially good point. The portions at Whispering Canyon Cafe are pretty big, even if you're not getting the AYCTE skillet and/or a bottomless milkshake. If your dinner reservations are early, I don't know how hungry you'll be if you had WCC for lunch unless you've got a pretty big appetite or plan to split an entree or something
Plus, it sounds like your plan is to go to MK in the morning, leave for lunch, go back to MK, go to Ohana for dinner. So I don't know how much time you want to spend in transit (though if you were spending time in transit, a nice boat ride to WL is a nice way to spend that time). But going to WL could easily be a 2 hour diversion at a minimum. Just be aware in case you were thinking about going back for the 3pm parade or if you have fastpasses.
My advice, grain of salt, is when you decide it's lunch time, gauge how hungry you are, what you've done in the day, what you still want to try to do. Then walk or monorail to Contemporary. If you don't want to take your time, or you're not that hungry, grab a little something at Contempo Cafe, then head back to MK. If you want a leisurely lunch, or if you're really hungry and want a whole sit down dining experience, go to The Wave, it's one of the underappreciated jewels of WDW. We make a point of going at least once every trip, but it's rarely if ever busy. While we usually have reservations, we've gone twice on a spur of the moment, and there was not a problem finding a table either time. But either way, when you're ready to go back to MK, it's a 10 minute walk, you don't necessarily have to wait for a monorail or a boat or a bus or anything, just go on back.
