Your first dates might cover the opening of the Food & Wine Festival at DCA. This year that ran from 3/02 to 4/12. F&W is lots of fun. For your second set of dates, check to see when the dates are released for the 2019 Grad Nites. This year, Grad Nites start May 4th. I would try to plan for the most days you can (so March 3-9 or May 6-12). That way you will have time to enjoy the parks at a more relaxed pace, including TS meals, shows, parades, live music, people watching, shopping, re-dos of favorite things, etc. And the extra day will also allow you to include a beach day or some other sightseeing, since you mentioned in another thread that you were interested in doing some non-Disney things, too. Your dates may not have the high season entertainment schedule (which means nightly entertainment will most likely be on Fridays, Saturdays, and Sundays), so keep that in mind. And there may be more refurbs scheduled during your dates, too -- just so you're aware of that. Easter is later next year (4/21), and peak Spring Break is usually the two weeks before and two weeks after the holiday. I don't know how early DLR will go to the high season schedule and when they would move back to low season.