Do you have a friend or family that will take him? The vet is probably the last place I would keep my bunny for more than a couple days and I am a tech. Don’t get me wrong, they will make sure he is safe and will take good care of him but he probably won’t get much time out of the cage unless they are a 24hr place or slow. I always feel bad for the animals that have to stay with us as they get little attention besides a hello and a quick head stroke when we pass by. Obviously the dogs go out to pee but they are not out long before they go back into the cage. Also a vet office can be very loud so if your bun is not OK with that it may stress him/her out. It never fails, we will get a dog here and there that no matter what will just bark nonstop. We have a isolation room behind glass for them but it is still loud. If the place is not 24hrs what fire protection do they have in place? We had a boarding facility by me that had a fire and a bunch of dogs died as the owners did not live on the premises and no one could get into the place in time. After that I never board my pets anywhere that does not have staff on the premise around the clock or lives on the property (with alarms in the house). I am a little nuts with my pets…..

As far as what to bring I would take anything that he has in his cage that will make him feel like home. They may not use it all but bring it anyway and let them know you want them to use what they can. It’s going to be a lot of new smells so anything that reminds him of home is good. I would definitely bring the litter box and fleece. The steal cages are a bit harsh and the fleece is going to slide around so you may want to bring something with a rubber backing or those super thin rubber mats to keep carpet in place for putting under the fleece. We usually put down towels/blankets for the dogs and cats but most of the time wont put anything in with a bun unless it is provided as we don’t want them chewing fabric if we cannot watch them (which is usually the case as we are very busy).