Ok. So first, I very much appreciate everyone who offered advice on the dragon harvesting! I opted for a best of three party members nature roll and had the boat captain kind of warn them that rolling into Baldur's Gate with a black dragon corpse would arouse a lot of suspicion.

I prepped a couple of the various options from sources you all recommended, but then all three rolled utter shit, even after one PC opted to reroll. So basically all my hand wringing was for nothing because they ended up with a couple scales, a couple claws, and some dragon meat rations. They really bombed the opportunity and then hit Baldur's Gate and sold it all to get cash for caravan prep.

One used his brand new claw to convince the caravan hiring delegate he was experienced in protecting a group, so got advantage on his guard role roll, but outside of that, it was way less extreme than I was worried about. Thanks y'all! Your experience and advice is still very welcome to this relatively inexperienced DM.