I've in the week of Easter before. Plan well. It will be busy. The year I went MK closed 3 days by noon--- for about 2-3 hours to offsite guests. We avoided MK until the very end of our trip. I will be the first to admit it was the least we've ever been able to do on a trip. However, we still had a really, really great time!! It's DISNEY afterall.
Use FP, this will help you get through at least a few major rides. Just be sure to start collecting them very, very early. As many may run out by lunchtime. Also, use EMH to your advantage. If you don't want to get up early, stay up late, or your offsite--- then avoid the EMH park as it will be busier. Don't forget to have some PS's. Most likely walk-up's won't be taken, so having a few is always a good idea.
I wouldn't cancel. If you go knowing it's going to be busy, then you'll do just fine.