I would watch Happily Ever After from the outdoor seating area at Trader Sam's and then walk up to 'Ohana. You'll hear the audio, see the broad strokes of the projections, and, most importantly, see the fireworks with no problem.
Contrary to a few opinions in here, I think a 9:40 p.m. ADR for 'Ohana is wonderful — we had one even later than that last time we went, and they sent us home with heaping boxes of leftovers. They have to get rid of all the extra food at the end of the night.