Roveer,
Your correct you dont want to be at WDW at Easter time unless you like standing in line for hours. MK maxes out around 10 in the morning on Easter weekend. It is crazy then.
We live 30 minutes from WDW and go almost every weekend and have 2 kids that work there so we know it pretty well. March is usually very good weather. We love it from mid October until around the end of May for weather.
We are usually in the upper 70's with a slight breeze every afternoon No rain or humidity. The summer months it rains everyday, very humid, and way too HOT in my opinion.
The only draw back to March is that it is spring break month across the U.S.
So it does tend to get busy at the parks. The middle, through the end seems to be the worst for crowds. Not as bad as Easter weekend.
But if you start your day when the parks open and use the fast pass system you should be ok. Also as a perk for guests staying on Disney property they have an early open hour at a different park each day. We avoid that park and go to one of the other 3 because 2/3 of the people there are at the early open park, which cuts down on the crowds at the other parks. I know that is reverse of what it should be, but it's true.
If I can answer any other questions for you please just ask and I'll try to help.
Good Luck,
mom x4,grandma x4