My experience with these high crowd weeks is to expect the lowest crowds first thing in the morning, with crowds growing through the day. At peak times in the day, expect to look up and just see a sea of people. Lines will be long. You may be able to get a fourth FP but not much more. This seems dire, but I'm planning a trip now for Easter week this year. It's all in your attitude and how you plan. Rope drop; use FPs in the late morning to early afternoon. You could plan to rest at the hotel in the afternoons, then return at night. If that's more for families with young children, then plan a long, leisurely TS lunch. In short, it's totally doable.
You're so lucky. How many high school seniors, boys especially, ask to spend spring break at WDW with their parents? This is a gift!