Getting ready to move across country, 1 day 4 hour drive. I'm sure they can handle the drive itself, but can they handle an elevation change that dramatically???
I figured my ducks will as they naturally fly pretty high anyway.
2800 ft isn't high elevation. You won't even notice, and neither will your chickens.
However, dehydration is a huge concern so you will need to be sure they get enough fluids. I suggest mixing crumbles with water so they get both food and water, but you will need to offer them plain fresh water at each rest stop.
Also, provide a non-slip absorbent crate bedding so they aren't sliding around in their poop. I suggest puppy pads laid down over a bath towel secured by duct tape so it won't bunch up.
Finally, a thin covering over the travel crates will calm the chickens and simulate cover to make them feel secure and safe.
Yes. I have gotten birds from a lower elevation and moved them to a significantly higher elevation with no major issues. Some of my ducks came from about 7,700 feet up to 10,000 feet, and did just fine (similar change to what you propose). Some of my pullets came from 3,500 feet up to 10,000 feet without an issue.
Just keep an eye on your birds for signs of stress in general, some are bothered more by the car ride and the move than others.