We've not gone in that timeframe exactly but a week later. And when we went it was surprisingly warm (80 degrees plus). But it wasn't a consistent hot. So if you want to swim, you may have to plan it as the temps may not be as consistent as you like.
Crowds are manageable for sure. Busy but not unbearable. You're right in the spot where the Spring Breaks haven't begun in earnest. It just requires a bit more planning is all. Be there a bit earlier, take some breaks midday, use your FastPasses appropriately, etc.
Being at BLT, you are also only about a 10 minute (or less) walk to the MK. And of course you have the monorail right there, too. So getting over to EPCOT is a breeze.