re: Yellowstone

Idaho falls, Idaho, Jackson, Wyoming, and Bozeman, Montana are the 3 places to fly into. All are small airports and similar in price and distance to Yellowstone. None of them are close, all around 1.5 hours away. Its slow moving out there, so if you are spending 5 nights that's going to be 4 days in the park which is honestly plenty. But I wouldn't plan to do much on the day of your arrival and departure as everything is slow.

You need to book your hotels asap as the best stuff sells out fast. There won't be much available inside the park even now. Expect to pay $200-250 for a Motel 8 type of room anywhere within 50 miles of the park. Its just how it is.

The towns of West Yellowstone and Gardiner are both worth a couple of hours. Most of the towns out there are. Its a great place to just take your time, road trip, and enjoy nature.

As said, expect all the big stuff in the park to be packed especially mid day. The best thing to do is to wake up early with a breakfast to go, then take a nap by a creek or great view somewhere and chill mid day, then enjoy the evening again.