First week of March is a perfect time to visit DLR! It may be cool in the morning and evenings but will (or most likely will) be plenty warm enough in the day to go on the water rides and enjoy yourself.
Flying from Maryland I would recommend taking Jet Blue into Long Beach airport. We have done this from Dulles for our trips - you get a non-stop flight that both times for us was wonderful. Long Beach is a great little airport - in and out and very California. If you have time, you can cruise around Long Beach and check out the Pacific (with a rental car of course).
Monday will probably be busier in the parks than Tuesday and Wednesday. If you stay at the
Disneyland Hotel, you will get Early Entry on Tuesday (unless they change it by then). You will definitely want to take advantage of this as park hours this time of year are short - park will probably close @ 8 pm those days.
Enjoy!!!!! You will love DLR!!