Kyle,
Temperatures in April, as per the National Weather Service website (
www.nws.noaa.gov), are;
High temperature: 83.0
Low temperature: 59.9
Average temperature:71.5
Monthly Rainfall: 2.42 inches
In my past trips we have skipped the water parks this early in the year, as we rarely get more than 1-2 good hours of pool weather. At that short of a time, using the resort pool is usually all we need. But that is your call, as you know how much pool time your family will need.
As to the best place to start, I am not sure what you mean. If this is your first Walt Disney World vacation, I always say that the first theme park moment should be entering Main Street, U.S.A. in the Magic Kingdom on the morning of your first full day. Don't rush here the day you arrive, and don't go to other parks until you have had this iconic family moment!
I hope that answers your questions! If not, please send me a follow-up question by visiting my bio page.
Have a magical vacation!