Hi Amy,
You should have no trouble getting to the Magic Kingdom in time for the Wishes Nighttime Spectacular above Cinderella Castle, even if you have a 4:30 pm dinner reservation at Teppen Edo in Epcot. Just enjoy a leisurely meal, exit the park through the front gates, and then board the monorail headed to the Ticket & Transportation Center. There, you will be able to transfer to either the resort monorail or a ferry that will deliver you to the Magic Kingdom.
However, I don't recommend that you try to experience the
Tomorrowland Terrace Fireworks Dessert Party and the Electrical Water Pageant on the same night. You'll want to take your time and enjoy the tasty offerings at the party. Don't rush away in the hopes of catching the Electrical Water Pageant. Plan that for another night.
My favorite place to watch the Electrical Water Pageant is from the beach behind Disney's Polynesian Resort. It is performed nightly at 9, weather permitting. If you have the opportunity, do try to work this experience into your vacation plans. I promise it will be memorable!
Best wishes for a magical trip!
Jill