There used to be an Illuminations cruise, but I don't know if they still have it.
Rose and Crown has reserved viewing for all patrons there at showtime (you can't leave when you're done and come back for the viewing).
They have an outdoor patio, where some of the tables have the best view of Illuminations. If you don't have a table with a good view (or are seated indoors) they have a reserved viewing area you can go out to, then come back to your meal after the show for dessert and drinks while the park empties out.
Last ADR time is at 8:00 for a 9:00 Illuminations, so an ADR at around 7:15 or later will make you the last party at your table, and then you get the viewing spot.