Try keep them in their hutches as possible.
You can also feed them Comfrey (Meant to reduce stress in rabbits) and Clover (A mild rabbit sedative). Try put towels or something soft under whatever the rabbits are travelling in, so if the van or car goes over a bump, the rabbit won't feel it as much. If they won't drink, give them some veggies dipped in water just before and during the trip.
Good luck x