I would suggest putting the 2 bunnies in a dog kennel that is smaller than their normal cage. Put something in the dog kennel that they can hide in to feel safer. Attach something with a lot of grip (like a small piece of carpet or fake grass). Make sure that the carpet of grass cannot slide around or be bunched up, SECURE it to the kennel. I will just warn you now that if they are not litter box trained you will have to (or want to) throw away the carpet or grass after each trip. A dog kennel helps your bunnies feel safer because most kennels are plastic and don’t allow in much light.

Make your bunnies sleep or at least spend a lot of time in the kennel a few days before your trip so that it is not as new to them and it kind of feels normal to them.

I would put the kennel on the ground in between the seats of put the seat belt over the kennel to secure it to your car so when you turn the kennel is not sliding all around your car.

Make sure they have hay and water, and you always have the car cool. Bunnies do not like heat and they cannot handle it (you probably already know that). Put them by an air vent if possible.

I would bring along their normal cage if it is possible if not don’t worry about it. Bringing along their normal cage is just a little thing that will make your bunnies feel more at home. Put the cage in a similar room that you have it in at your house and try to make everything in the cage the same.

Hope I helped. Good luck.

If they are bonded, it will probably be easier on them.
The carrier should be covered on three sides – buns get scared of things that flash by. You should line it with soft fleece and puppy-pads underneath to sop up pee. Bring extra blankies so you can change if they get dirty.

You will probably have to stop for eating and drinking. There should be hay in the carrier and a waterbottle. Bring a water bowl for when you stop, many buns won’t eat or drink in a moving car and they might think the bottle is too much work. You can bring fresh greens (dandelion, parsley, cilatro, romaine) that you can dip in water to help them keep hydrated.

If you leave the car you have keep the doors open the doors etc so it doesn’t get too hot. Even a quick stop can result in a very hot car in the summer and buns don’t do well with heat.