I think this depends on your tolerance for crowds and possible heat. If you give yourself plenty of time to research and plan (and you can be flexible), there's no reason why you couldn't have fun in the parks. Be aware, though, that fireworks at that time may be projections only on weekdays.
Heat wise, our tolerance is fine.
Crowds - not so much. We come from Australia, so really do try and plan our trips around crowds (since its a once every few years trip). We were last in the park January 2020 and it was incredibly quiet.
Was hoping end of September would be quiet.
Fireworks aren't important to us at all.