I think you have a really nice outline for a plan!
You said that in your first trip, having every minute planned added to your stress. What I would suggest is getting a feel for what attractions are best to visit in what parts of the day. Some things are rope drop or FP only, some are 1st hour, some are anytime before lunch, and some are anytime. That way, you can have a general plan without a "at 10:13 we will take two minutes to walk to Dumbo" plan.
With regard to your specific plan, I have just a couple of small suggestions. 1) I am pretty sure that Anna and Elsa are only in the Magic Kingdom and no longer at Epcot. Meeting them is a rope drop or FP only attraction as the lines are VERY long.
2) On March 18, you have your Buzz FP in the 1 PM hour. This was the favorite attraction for both of my boys when they were 2. However, that is prime naptime/I missed my nap meltdown time. I would put that FP in a time where your 2 yo is in a really good mood.
3) You don't have a time for your Biergarten ADR, but remember to allow at least 90 minutes (I would allow more) from the time you leave MK. It is a LONG walk back to the Germany pavilion.