Edward,
Thanks for the question to planDisney!
With your park ticket and a
theme park reservation, you can enter, exit, and re-enter that primary park multiple times throughout the day. It is great if you want to leave the park to get some pool or nap time for your family back at your resort hotel. It is also nice if you want to head over to a resort to grab an entertaining meal. We often will leave the
Magic Kingdom Park to have dinner at
'Ohana, over at
Disney's Polynesian Village Resort, before heading back to watch the fireworks.
As for Park Hopping, you could also enter, exit, and re-enter a secondary park after 2 pm in the afternoon. However, do know that to enter or re-enter that second park it would have to have open capacity. I have never run into an issue getting into that second park when I hopped, though during extremely busy times it could happen.
BONUS TIP Be certain that your party has the
My Disney Experience App loaded onto their smart phones before entering the parks. The
Disney Genie service you mentioned is great at providing activity suggestions, as well as helping you with locating and ordering counter service meals with the
Mobile Online Ordering service.
Have a Magical Vacation!
Doug