Hi Sue,
The first part of your question is easy - Yes! There are fireworks nightly in both the Magic Kingdom (Wishes) and Epcot (Illuminations).
The second part of your question is like asking me to choose my favorite child. I love them both, but on different days, I like different shows better (just kidding!). As a mother of an 11 and 8 year old boy, I figured they were best qualified to answer your question. Their vote? Without hesitation, they both answered Wishes!! Although they like Illuminations, Wishes is more of a traditional fireworks display set to music - it's everything you like about a 4th of July display, only better.
They are completely different experiences, and I recommend seeing both if you can fit it into your touring plans.
Also, are you planning on going to Hollywood Studios? This is my boy's favorite park, and Fantasmic! is a nighttime show that I think your whole family will enjoy. It only shows on select nights (usually Sunday & Thursday), so check
HERE for more information. Just click on a date to see an entertainment schedule for a specific date.
Hope this helps. Have a magical vacation!