We stayed late and our 18 month old loved the fireworks once I covered his ears. We picked a spot where we could both watch the Tapestry of Dreams and IllumiNations.
Find a spot early, it can really get crowded.
Don't head for the exits after the show it is really crowded. Find a place where you can shop or grab a snack for about 30 minutes.
Pros: Fireworks, Music
Cons: Crowds, Noise