Hi Ceciline,
I love the
Park Hopper Option for Disney World tickets because it allows you to experience as many of Disney's four theme parks as you desire in a day. Your feet may be your only limitation because your ticket is not.
You can go to
Magic Kingdom,
EPCOT,
Hollywood Studios, and
Animal Kingdom as many times as you want during the day of your ticket subject to capacity limitations. If a theme park is already at capacity for the day they will no longer allow park hopping to that theme park to ensure the safety of everyone there. This typically only happens during the busiest times of the year and on holidays so should not be an issue during your visit in May.
The answer to both of your questions is yes, but I would caution you that transportation between theme parks can take up to an hour depending on what methods of transportation you are taking and how far apart the locations you are visiting are. Since your plan only includes 2 theme parks, you may get much more out of finishing all of the activities you want to do at the first theme park before heading over to the second one so you don't waste too much on your day just going back and forth. That also may leave your options open for visiting a third location after dinner!
I would take the time to review the
transportation options between the theme parks you are looking to visit before making a final plan. For example, transportation between EPCOT and Magic Kingdom or EPCOT and Hollywood Studios are both super simple and don't take up a lot of time. However, if you are headed to Animal Kingdom from any of the other theme parks that can be quite a trek.
Happy Planning,
Jenna