According to Google, sunset in November in Orlando is around 5:30pm. I guess it depends on how long you want to see AK at night. (It is very beautiful, although some areas are not well-lighted, so don't try to move too quickly.) If you're planning to do FOP again, that alone could take up to an hour depending on the wait (and if you're visiting during Thanksgiving week, more like 90 minutes). Assuming you're there on a non-holiday week, I'd allow one hour for walking the park, one hour for FOP, and 45 minutes (way more time than you need, but a cushion is always good, especially at closing time) to get from AK to AKL if you're taking the bus. That means you'd want to arrive at AK by about 5pm, and do FOP first, so that by the time you're finished, you can exit into the glowing wonderland that is Pandora at night.
If you arrive early for your dinner reservation, enjoy the beautiful lobby and grab a drink at Victoria Falls Lounge, which overlooks Boma. It can get loud, but if you don't mind the noise, it's a very pleasant spot.