Trader Sams opens at 4pm, so you could arrive early and experience the special effects in the bar before your Ohana reservation. I believe the Poly still has a torch lighting ceremony in the early evening (think Hawaiian man waving flaming torches around and then symbolically lighting a lamp etc). After dinner there will usually be an outdoor movie on the green at the rear of the lobby, or you could get another cocktail on the outdoor Trader Sam Terrace, listening to Hawaiian music (sometimes live) and watch the Electric Water Pageant from the Terrace, or head down to the beach area.
One thing to consider when making plans is that seating for Ohana reservations often run late for some reason so assume you may exit the meal later than you would normally expect with a 6pm reservation.
