Hi
Raymond! It is very difficult for me to choose between the theme parks as each has its own unique flavor and charm. The same can be said about Disney fireworks displays. If I was traveling with children and only had 2-Day Magic Your Way Base Tickets, I would choose to visit Magic Kingdom both days. For my family Wishes Nighttime Spectacular in Magic Kingdom is an absolute "must do," at least twice during each visit. However, if your heart is truly set on exploring one other Disney park, I would recommend Disney's Hollywood Studios. Be sure to visit this theme park on a Fantasmic! night. I suggest you read more about the 4th of July celebrations at the Walt Disney World Resort
here. One option would be
not to visit the parks on either the 3rd or 4th and instead opt to watch the special Magic Kingdom fireworks display from outside the theme park. There are some very nice dining spots and other locations where this can be accomplished. Read more about it
here. If you choose this option, I suggest booking Advanced Dining Reservations at 'Ohana's. The beach at Disney's Polynesian Resort will afford your children the opportunity to play outside while simultaneously being able to enjoy the spectacular fireworks display. The show's audio will be piped-in through several ground-level speakers along the sidewalk. Book your ADR by calling (407) WDW-DINE or
online.
Please let me know if I can answer any other questions for you. Have a memorable visit to the Walt Disney World Resort!