We've been to Disney 5 times, and did not see the fireworks until our last trip, when we stayed at BLT and could walk back. Coincidentally, that trip was the week that Wishes ended and HEA began, so we saw both shows for the first time on the same trip.
The fireworks were great, and we all really enjoyed them. However, we loved our previous Disney trips as well, and never regretted missing the fireworks. When we finally saw both shows, I actually enjoyed Wishes much more than HEA, but we had prime viewing for Wishes (dessert party); whereas we watched HEA from our room at BLT, and I think you need to be in the park for HEA to truly experience it with all of the projections.
We have young kids (5 and 1.5) and I have no interest in being packed into Main Street like sardines for a show that they probably won't be able to see very well, then fighting the crowds to get on the monorail/bus/ferry when everyone leaves the park after the show. So, we won't see HEA from MK on future trips unless we stay at BLT/Contemporary and do a dessert party.
In your situation, I personally would not regret missing the fireworks. It's hard for me to imagine that MK won't be significantly less crowded than usual on a day that closes at 4:30(!), and MK will definitely be VERY crowded on non-party nights, since the opportunities to see the fireworks are limited. I think when we're on these boards, it's easy to get caught up in things that we MUST do, but there are no "must-dos". It's a vacation. You're at Disney. Even if you miss the fireworks, you will still have a fantastic trip.