Hi Melissa!
I know exactly what you mean! I'm in the middle of planning my June trip and it's sometimes tough figuring out where to go, what to eat, and when to ride. My personal thinking is: Get as much information about the dates you are going and then plan around the events. You seem to be on the same page. Unfortunately, I do not know of a master schedule on the Walt Disney World site which highlights every event at once. All of the planning that I have done through MyDisneyExperience on the website has been very helpful but also a bit time consuming.
I do know some of my fellow Moms Panelists that utilize the Travelingplans.com website and seem to really enjoy being able to use some of their planning templates. You could also look at the Allears.com site which has great information about upcoming events and schedules.
For the end of March, one of the major events that I do know about is the
Epcot International Flower and Garden Festival. I would definitely try to attend this event as it's included with your Epcot ticket admission and features some of the best topiaries you will ever see!
Thank you so much for asking the Moms Panel! Please let us know if you have additional questions, we are always here to help.