Here's a funny idea I had... what if the celebrations were before the funeral? I think it might work, given the proper editing. Make it so that it's almost as if the ghosts of the three Jedi are reminding him that he has a duty to dispose of Vader's remains. Also, it would feel darker IMO. Besides, Luke seems the type who would skip out on the celebration for at least awhile for some alone time. That is, if the teddybear parade were used instead of the world celebrations - I'm in the minority, but I prefer that to the celebrations (not the music mind you, the celebration).