We went last year when our boys had just turned 4 and 2. We had 5 park days. Spent 3 at MK, one at AK and one at HS. I'd do it again that way in a heartbeat. Our boys were definitely happiest at MK and enjoyed every day there. We spent a full day at HS, mostly because of show times...we didn't do much. Started with breakfast at Hollywood & Vine (both boys LOVED it), rode Toy Story with a FP (we were there the week they did a fast pass only test so were only able to ride once...otherwise, we would have gone straight there after breakfast, which was when the park opened, so we could ride twice), then waited in a long line to see Woody and Buzz, saw the Disney Jr show with FP, ate lunch at 50s Prime Time (I personally wouldn't do that again), went back to hotel for nap time, came back for Frozen Sing Along with FP. Some down time and just wandering around to kill time between scheduled attractions. We would have seen more characters but had already seen most everyone at MK by then. Anyway, just my experience with boys close to the same age as yours.
We also did CRT for breakfast. The boys liked being in the castle and getting swords, but that was about it. My oldest isn't to the point where he thinks princesses are just too girly, but he only posed for pictures with them when they came around to the table because we let him hold his sword in the photos but wouldn't let him touch it while eating. Food was ok. I kind of wished I had a girl with me to watch her get all excited about meeting the princesses...that would have made the experience much more magical. We won't go again most likely, but I'm glad we did it.
I never once wished we had done Epcot. We will be back in a couple of years when they're older but still young enough to like doing most of the "little kid stuff". They were so overwhelmed by everything else - and don't even know Epcot exists - that they were perfectly happy with what we did. And my oldest is a ride weenie, so there's really not much at all there that we would have done anyway.
More info than what you asked about, but I always find it helpful to hear about others' experiences...hope you do too!