Well...my kids are older now, but looking back....
1) Character meals - kill 2 birds with 1 stone. Ya gotta eat and lines for Princesses, etc are insane. Just spend the $ on character meals and be done with it. Must book 180 days in advance at the crack of dawn.
2) Rope drop. Just do it. As another poster stated, rope drop and hit a couple of rides with no fastpasses so schedule your FP starting around 11.
3) Afternoon parades - If you're not going to go back to the room in the afternoon, some down time in the stroller eating a dole whip watching the parade is a nice re-charge. And a wave from Tinkerbell just might suffice if you don't get the meet and greet done.
4) Consider a stay (or split stay) at a monorail resort and Epcot area resort. BLT will give you the option of walking (pushing a stroller) to/from MK. BWV or BCV are walk to Epcot and HS (BWV being more in the middle). Plan your MK days during the monorail stay and your Epcot / HS days at the other. This saves tons of time on transportation, which IMO is the biggest time-suck of them all. You can rent points at DVC resorts for about the price of a stay in a moderate.
If you are talking about THIS December (2 months from now) you are probably out of luck on the DVC rental and possibly the character meals. Get those FPs! Disney takes planning really really really far in advance. Unfortunately.
I have never done EMM so others can chime in. I'd hope that that will enable you to accomplish a lot and you can take a relaxed pace after that.
All that being said, I took both my girls for the first time at 3 y.o. and it is the most magical time! I believe that set them up to be life-long Disney lovers. They are 16 and 20 and always wondering when the next trip is.
Have a great trip! We will be there this Dec and are looking forward to our first
MVMCP!!