I think you booked it for a reason, so you should keep it. If everything goes according to plan, it's a win. If it gets rained out, consider it a learning experience.
We did the package a few years ago. And while the overall night wasn't bad, we wouldn't do it again. As we opened the door to leave HBD and head to the theater, very bright lighting, very loud thunder and heavy downpours started. At first they kept announcing that the show was delayed, but eventually it was cancelled. Fortunately, this was back when both appetizer and dessert was included, which actually worked out to be less expensive than if we had just had dinner at HBD.
Luckily, we hung around the park as the rain lightened up, waiting on word if Symphony in the Stars (I think that was the name of the Star Wars fireworks before Galactic Spectacular) would go off, which it did, with what seemed to be about 200 people who refused to leave the park with us.