Setting: Okay, so you've got a pretty major challenge here, if your brother and/or friends are LotR-nerds. Gandalf, Elrond, and lots of other folks sail away into the West at the end of the Third Age. So either in your game, they didn't leave (or didn't leave so quickly) or maybe you move this back into the Third Age, which makes the Palantír a bit tricky, but not insurmountably so.
Okay, I'm going to go through your outline and make some comments.
Intro: I'd try to cut this down as much as possible. Open in-media-res with the heroes in council with Elrond. There's no need (mechanically) for a shopping trip, and I'd be leery (especially if they're coming from a more gear orientated game) of encouraging them to prepare too much. All the prep can be dispensed with a single sentence, which gets you closer to rolling dice.
Travel 1A:I'd insert a simple Journey here. Elrond's already told them to meet the scouts at X location in the Trollshaws, so you can have everything precomputed. Roll a few Travel tests and use this to explain how the basic mechanics work. Remember, like James said, do the Preliminary Roll first.
Encounter: This seems like a good idea. It should be a low-stress Encounter, but give the heroes a chance to gain some benefit from it (like maybe there's a Snow-troll den they are told about, that they then can avoid, or maybe the Rangers' advice gives them an extra Bonus Die when it's time to do preparation.
Travel 1B: I'd continue this as part of the original Journey, with the Rangers being a prepared Encounter and then the Wild Wolves and the Wolf Leader being a prepared combat.
Gandalf Scene: The idea of the Palantír kind of comes out of nowhere. Maybe have it be a bit more explicit... there's something terrorising the countryside and it finds even the hidden caches of the Rangers. Gandalf suspects some powerful magic at work.
Travel 2: Sounds good. Be cautious of too many Hazards/prepared events, but I do think you need to have some things for the heroes to interact with.
Carn Dûm scene: You've got Ruins, so you've got Jon's awesome map of Carn Dûm. I wouldn't get too bogged down, but it might be worth doing a few Explore/Search/Awareness rolls to explore the dungeon a bit. Dragons don't really have colour in Tolkien (they do, just not like D&D), and in theory your winged dragon is a bit of a discrepancy, but no one has all the facts and the narrator of The Hobbit could easily have been wrong about Smaug being the last winged one.
Meanwhile, Gandalf is hunting for the Palantír. Maybe it was one of the Northern Stones, recovered by some evil thing from the northern seas. Again, this gets tricky, but you can certainly make your game work however you like and don't need to feel bound to canon.
Encounter with the Dragon: If you've got Tales from Wilderland, take a look at that for inspiration with this encounter. It certainly should have a chance of turning very bad. I'm really not sure about the whole 'riding the dragon' thing, but it certainly could happen... the Steward could have fitted him/her with a saddle in an attempt to tame it.
Final Combat: Sounds very epic. My only real concern is that it seems like you've got a strong vision of an end-scene and sometimes that can be a bad thing... railroading the players to get to foreseen end point can sometimes be very frustrating from them. I recommend that you be prepared for things to go odd, especially once you let them loose in Carn Dûm. Maybe if they decide to search the dungeons instead of fool with the dragon, they can end up finding the spell to unbind the Wraith's physical form, and Gandalf gets to end up riding the dragon
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Jacob Rodgers, occasional nitwit.
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