I think a lot of people stress about transporting buns long journeys, but on the whole I think the majority of them cope absolutely fine! My frenchies had a 5/6 hour journey home with us and when we got home they hopped out of the carrier and started exploring like nothing had happened.
Couple of things I did to prepare them was;
Find a carrier that was too big, so that they could lay seperately of each other if they got too warm (they stayed huddled up the entire time!)
Put the air con on
Some wet veggies to put in half way through and a bowl and water bottle to offer them water (don't put a bottle in as it drips with the motion of the car and soaks the carrier)
Didn't fuss them (strokes etc) as may stress them out more, just left them to it
Had all their setup ready go to (minus fresh hay in the trays which took 30 secs when we got home), put their carrier in and let them come out in their own time without us around (we were outside looking through the mesh door
)
Also might be worth taking a bit of hay from their old setup so they have something familiar? Although probably less relevant when theres two bunnies as they have each other
Good luck!!
Oh and I regularly take the Frenchies to and from the specialist which is 40 mins away, so they are often in the carrier for 1hr+ and aren't bothered at all