It will be busy. Make ADRs for any table service restaurants you want to eat at and definitely plan on using FP+ strategically with rope drop if you want to get on the big rides with the least wait possible. However, I have gone during spring break and it is doable. Crowds to me don't feel that much different than summer. Or December. When I went in early December, lines were just as long! I'm not sure there is any slow time in Disney anymore...