You're all welcome! Any help I can give to other families so they can get the most out of their trips, I will!!
About the stroller, yes it can be difficult at times maneuvering with a stroller, but it really doesn't slow you too much. With a 4 year old, I say definetly get one. This is the first year we didn't get one, and my kids are 6 & 7. They were pretty tired by 5 or 6 pm, and the rest of the evening we heard about it(!)
We did go to the MK on Friday and I have to say it was the busiest I have EVER seen the park. The mid afternoon hours it was extremely difficult to walk due to the sheer volume of bodies and every single ride had a line of at least 45 minutes. it was unbelievable!

One of our biggest obstacles was the fast pass spacing. It used to be you could get a new fast pass an hour after you obtained the last one, now it is 2 hours....meaning unless you will be in the park 12 hours you can't get a FP for everything...which altered our plan of attack.
Some updates and clarification on my earlier post:
Peter Pan...If you want to ride it, and if you have younger kids- get the fast pass. I confused PP with Snow White Adventures, PP does have a longer line as it has the flying "boats" with smaller capacity. We actually didnt get on PP this visit since we had to get selective with our Fast Passes only being able to get them every 2 hours. We decided to forgo a FP for PP and found the line never did subside...even at about 10:30 pm it was still 40 min

Though I can safely bet the crowds when you go will probably not be as bad as Spring Break (for many) Good Friday. I can say we have never seen lines like that, ever!
We did arrive earlier than most times (9:06 in the parking lot, inside the park at 9:30)...and found Fantasyland with pretty light crowds. Dumbo was 30 minutes, with only half the queue open, though by the time we got off the ride, the wait was 60 minutes with the line full queue and around the ride perimeter. (whew)

Here is an aerial of FL from Dumbo taken at 10:06 am.
You can see the crowds are still light (yes, that is very light!). The FP we had gotten were for WTP with an early return (11:55-12:55). Becuase of that we did not follow our "usual" plan and stayed in the Fantasy land/liberty square are until early afternoon.
One thing I can definetly say is that the wait times posted outside the rides were way overstated....a "20 minute" posted wait for Snow White was only 5-8. 30 minute posted for Indy was less than 10. 60 min posted for POC more like 20. Space Mountain had a 120 min posted standby (we did not manage to snag a FP for SpM...they ran out by early afternoon) but thankfully we were off the ride in 59 minutes exactly (we had a bet on it!)
We noticed a huge lull at parade time, SpM wait was only 40 mins (and we were kicking ourselves for not taking advantage of it later!) Here is an aerial of TL taken from the people mover at 2:41 pm, the low crowds evident by the visible cement ground..earlier it was a swath of humanity as far as the eye could see
We did a few things we don't normally do, having extra time due to the extended park hours. We checked out Tom Sawyer Island and the kids loved it, there is an "escape hatch" tunnel that is a lot of fun, plus the barrel log bridge:
Its all walking over there, and a lot of climbing too, so do it early in the day before everyone is so tired!
It was also our first time seeing the Philharmagic which is a don't miss for the kids, really enjoyable. Also the new Monsters, Inc. "Laugh Factory" is now open in Tomorrowland, across from Stitch where the Timekeeper used to be. Like a stand up comedy show, it features audience interaction and you can text jokes in from your cell. Have a good quick joke ready to send in, they only pick the three best ones! They also show select audience members on camera, in our experience it was all people from the front three rows (stay to your right when entering the pre-show building (after the queue room) to enter the show room in the front. The kids loved it, and it was quite amusing.
We didn't do as much backtracking as usual, due to the fact that the availability of the fast passes was limited by the 2 hour gaps. We only got Fp's for WTP, BThunder Mt, SplM, and Buzz, JC, and BTM again, in that order. Everything else we rode standby, with the longest wait being 55 minutes for SpM. IASW had unusually long lines all day averaging 30 mins (usually a walk-on no wait ride)...the Pirates queue and stroller area has changed, with the stoller area being to the left side of the ride now and the queue roped off and snaking in the area under the overhang where stroller parking used to be. HM does not offer FP anymore, but we lucked upon only a short wait at dusk, just like I like. The haunted mansion at appears its creepiest:
As the night parade time approached, FL emptied out a bit, and we got on IASW aith only a 15 minute wait, it was at 8:45, which I know since I got a pic of the clock going off:
We headed over to SpM thinking the line would be lighter, but nope. Right after getting off we got to see the fireworks, still easily visible from that part of the park!
ALSO keep your eyes open for this: While in ride for Dumbo (early am) we saw a family with lanyards and a plastic "pass" with little plastic break-off tabs on it. It said it was a "Dream Fast Pass". The little tabs were Fast Passes for each ride that offers it, and could be used at ANY TIME during the day!!!! We asked where they got it cause we would have paid big $$$ for it, and they said that a CM HANDED it to them on the carousel right before they got in the Dumbo line! It appears to be a random thing, only available to the poeple on that ride at that time. When that lady asked to get one for her husband who wasn't on the ride, they said no. We only saw about 10 people with those, so it is obviously not a readily available thing, I guess you have to get lucky. (Maybe it wouldn't hurt to try the carousel at 9:30 am...?)