Well, the timing can vary greatly. If you use the resort monorail, best case - a monorail pulls in when you are walking up to the station, then it makes the two stops at CR and TTC and gets you to Poly in about 15 minutes. Worst case - you just miss the monorail and wait about 10-15 minutes for the next one, but then they need to bring another monorail on (or take one off) and you wait 20-30 minutes for that to happen before your monorail can even move, and then you have the 15 minute ride - so you could end up with an hour.
If it were me, and I didn't want to miss my meal, I'd be inclined to use either the express monorail or the ferry and walk from the TTC. The express monorail goes away from the switch where monorails come on and go off the beams which minimizes that possibility, plus there aren't any other stops between MK and TTC. The wait is longer sometimes for the ferry, but you can kind of eyeball it as you exit the park and if there is one just about to pull in, go for it. I would say the express monorail would be at maximum a ten minute wait and a five minute ride. The ferry (if you catch one just coming in) would be about fifteen minutes or so. Then allow 10-15 to walk from the TTC to the GCH at Poly.
Unless MK is having EMH that morning, you aren't going to be able to do much before you leave the park. I would allow at least 30-45 minutes regardless of what transportation you choose.