My daughter is 2 1/2 and we recently had a long trip as well. They let me take my buggy through security but I had to take her out of it and fold it up to run it through their scanner. Then when we boarded the plane they stowed it underneath. When we got off they gave it back at the gate so I didn't have to wander around without it. That was a huge bonus going through customs... which fortunately you won't need in Alaska.
Anna was so excited that the first flight she didn't sleep a wink... that was 4.5 hours. The second flight was 10.5 hours and she only slept for an hour here and an hour there. If you purchased a seat for your daughter, bring her car seat. Put her in the middle of the two of you. If she is sitting in you're lap, they will give you a crazy looking seat belt for her to strap to your seat belt for landing and take off. I broke up the legs of our flight so we stayed in a hotel over night between flights. That made our journey so much more comfortable.
I am not sure if your daughter has teeth or not, but I gave Anna gummy bears to help with the pressure. If you are nursing or she still uses a bottle that will work too. They should let you guys board first so you can get her settled in. The stewardesses were very helpful, they let us walk up and down the aisles as long as she was holding my hand, and as long as she was happy, some of the passengers would play peek-a-boo with her as we wandered around.
Diapers have to be disposed of by you in the lavatory, the stewardesses are NOT allowed to touch them, and they are not allowed to let you dispose of them in their waste baskets either. They aren't being rude, it's a rule because they handle food. Bring a few plastic grocery bags in your diaper bag to stuff them in. I changed Anna in my lap rather than trying to struggle with the bathroom. If you call the airline ahead, some planes have basinettes in bulkhead for nap time, those work well for changing too. If you are lucky you can sit there and you will be able to use that while you are in flight if your daughter falls asleep.
Quiet toys are much better than noisy ones on a plane. Bring extra snacks, ours ended up not going as far as we had hoped, but the stewardess was extremely generous with her stash. Also you will need extra clothes on the plane for each of you. I ended up wearing almost as much juice as Anna. Plus an extra bag for dirty clothes.
If you are staying in a hotel, ask for a crib... most of them will provide one. If you treat it like an adventure, you're daughter will too, so stay positive!
Have a great trip!