I’ve found out over the just-concluded Thanksgiving-Christmas holiday season that my own two buns do quite well with fairly lengthy drives (400 miles or so, approx. 7-8 hours on interstate highways mostly), with regular stops along the way to check that they’re reasonably comfortable as Q8 and Mikey advise. A very good thing to do is to offer them wetted-down greens an hour or two before you get on the road, which gives them plenty of water and pretty much eliminates the need to put a water bottle or something of the sort in their carrier. I have another trip forthcoming all the way from Virginia to South Carolina and back, though, in the spring, which may be inconvenient to bring the rabbits along on, but we’ll have to see. It should be much easier to find pet-friendly motels/inns along the road route to California than to deal with airlines, and probably cheaper too; and a three-day drive with overnight stops along the way each evening, giving your buns time to relax before the next leg of the trip, taken along reasonably good-traffic roads, should be a lot less stressful overall than air travel.
P.S. I’d recommend finding a good carrier large enough to hold your three buns reasonably comfortably, if at all possible. Being with each other in a fairly roomy carrier with a well-found litterbox placed inside with lots of hay and litter eases the discomfort and reduces the stress for my own two a great deal.