Everyone tours the parks in different ways so difficult to tell you if 3 days will be the best way for the 3 parks
I have 4 different friends that spend at least one half of their park days in the potter sections
They cover all the live shows and each shop + rides there
For me, I do the potter rides and go to the ice cream shop and hit the main restaurants in them
Then I move on to the rest of the park
I enjoy my time there but can cover what I like to do there in a couple of hours
If your husband is a potter fan, a few hours won't be enough
If you check out the website and decide what rides, shows, entertainment you want to do each day, you can cover a lot
Just plan ahead for the must do items on your list
Two days for the 2 parks can work out
as long as you are not going in the summer months
Be aware that rides can go down and you can either wait in the line or return to it later that day
When a ride goes down near closing, don't count on it being back in service that night
Sometimes planning for four days in the park works well
It gives you plenty of time to redo rides or do the parks at a slower pace
We all do the parks differently
Go with whatever works best for your family