I live in Orlando, Disney is always crowded, Disney is always amazing!! You will have fun no matter when you go, there will never be a time that it is not busy. We go at least twice a month and my girls go crazy for it all the time. The lines can be long, but there are fast passes, but many of the kid rides have enough going on in the line to keep kiddos entertained. I would advise you to pack snacks and juice boxes in a backpack, snacks are great for longer lines.
If you want to check the spring break dates you can google Orange County and Seminole County public schools and look at the calendar for next year. For the past few years our spring breaks have not been near Easter, and the college is even earlier.
You will have an amazing time no matter what, the more you stress about it the less you will be able to enjoy it. :)