I think your plan is most doable! For HM, there are no special scenes but after Sunset, they start pumping fog, has special lighting, and usually there is a ”ghost” in the graveyard that interacts with guests. Getting a pic is pretty awesome as there are usually special “magic shots”. Lots of great trails and towards the end of the party, we’ve had tons of candy just dumped into our bags Which were completely full after just a few trails. Since there are 2 parades, I’d plan to do SDMT during one of them. Last year my mom (who’s in her 70s and uses an ECV) did the treat trails, saw the 1st parade (viewed from main st), the fire works, did a few M&Gs (jack sparrow, the twiddles, and am forgetting the last one), did a bu ch of photopass pics), rode HM, SDMT, IASW, people mover, BTMRR, POTC, actually had ADRs for LTT and ate dinner there (would not advise doing that! Took too much time), had some of the party-only treats. And I think we left before the end of the party. So we did a lot! We entered the park around 3pm with our reg. tickets. But we generally just did some shopping before dinner, picked up our party wristbands,a nd walked around a bit.