I will give some Potter hints.
Expect to spend at least a half a day each in Hogsmead and Diagon Alley. If you purchase an interactive wand, there are many places to use it and you can spend hours finding them all. Some are easier to view at night, so try during different times of the day. Be sure to watch the shows in Diagon Alley. Also, the ice cream is wonderful. So many different flavors! We grabbed a cone and watched the Tales of Beetle Bard.
Make sure you have a park to park pass. You will need it to ride the Hogwarts express. The ride experience is different each way, so make a round trip. The food in the WWOHP is delicious so plan on at least one meal at Three Broomsticks and at Leaky Cauldron. There are no dining reservations available for WWOHP, so no need to preplan.
Really take the time to go through each shop. Fans of the books will find amazing details that are easily missed.