Easter week is super busy at the parks. To really enjoy the day at Universal on April 2nd would be if the ship was getting there early and you can be at the park at 10am AND with a fast pass.
The Fast pass on that day is an additional $70. per person.
Since the fast pass is priced that high on that day they are expecting lines and lines of people. I bet the wait for Harry Potter will be well over an hour. And the fast pass does not apply to Harry Potter. Fastest way to do Potter is going on the single rider line.
have an awesome cruise!