At the Galactic party, there is seating at the party inside before the show. Limited, but it is there, including some sort of in a courtyard (saw people sitting there as we left).
But one huge advantage of galactic is the available handicapped section, for the party goers. My son is in a WC and it was a real blessing. It is not for kids in strollers. Some have reported that they allowed kids into the section right before show started, but this did not happen the night we went, it was full with WC guests and their families. And leave a bit early to get a spot.
I thought you could sit at the MK fireworks party, the one on the patio. Another option with a group is to get one of the cruises to see the MK fireworks or Illuminations, sitting available on those, lol.