Thank you for caring about these cats. Can you tell us anything else about them? How old are they? Where are they located? What are their personalities like? Are they bonded to each other?
This is an international site so I don't know if you will be able to find someone here to take them. Do they have a vet that they use?If so, can you ask the vet to post pictures of them letting people know that they are available for adoption? Are they up to date on all of their shots? If push comes to shove, do you have a local no kill shelter that can take them? Please do not post them on Craigslist unless you plan on asking for a rehoming fee. This separates the ones who are serious about wanting a cat from people who would take them for more sinister reasons. Unfortunately, this does happen.
Does the owner have a Facebook page? If so, he/she can post pictures of them on their page and let people know that they are looking for a home. This way, they can try to give the cats to someone local that they already know.