how large are the fish? if your just transporting medium sized cichlids, a bucket will do just fine, if your worried, bring 2, six fish in each, 30 minutes isn't a long time.
also half way through, you could try scooping some water out then pouring it back in, this aerates the water.
one more thing, try and keep the buckets covered, this will help retain heat, do anything you can to insulate the buckets, covering the sides with fleece blanket does this very well.... good luck, i wouldn't be too worried about it, sometimes i think ppl stress more than fish do during moves. (not to say its not stressful for the fish, but its not that bad.)