I think AK usually closes at/about 5pm but is open later for extra magic hours some nights (available if you stay on Disney property resorts). I think the extra hours could be great for having dinner in AK park after dusk. Otherwise, Tusker House and Yak and Yeti seem to close when the park closes.
For us, there's not a lot to do during extra magic hours except the dinosaur ride so dinner would be a good option. There are some other rides/shows open during extra magic hours but our plans have been to get to AK early in the morning so we are usually done most everything we want to do by 5pm anyway.
If you have park hoppers, why not hop to another park like MK or Epcot for fireworks? If no hoppers, take a bus from AK park to one of the monorail resorts (Contemporary, Polynesian, Grand Floridian) for dinner and watch the MK fireworks from there. We like the Polynesian beach for watching MK fireworks. Then, to get back to your resort, hop back on the monorail to the Transportation and Ticket Center, and catch a Disney Bus.
Last trip, we left AK park to go to AK lodge for dinner (Jiko). Didn't take long at all (10 minute ride?). I was suprised that DS4 hung in there with us for a long dinner. The gift shop there is nice (a lot of the same stuff you see in AK park) and there are some special activities (night viewing of animals, story telling around a fire pit) at the lodge. We took a taxi back to our resort because Disney buses don't go from there to other resorts.