Joy, I understand your worries as I am currently trying to figure out how to take my ancient mutt in the other direction.
First off, having moved my dogs around the world many times I am of the belief that my pets are always better off with me. Losing the family who love you, adjusting to a new life - especially in the twilight years - is far more stressful for our pets than 12 or so hours of flying would be. So I would try to bring your cats along, assuming the vet OKs them to travel.
How big are your cats? If each cats plus carrier are under 8 kg (airline dependent), you can take them in the cabin - so no worries about the discomfort/dangers of cargo.
If each cat plus carrier weighs more than 8kg (airline dependent), then it has to be cargo. If that is the case, I would use a professional pet shipper to plan and oversee your travel. While I have not needed a shipper recently, I've corresponded with this gentleman, and came away with a very good impression of his service:
http://www.acepetmoving.com/en/about-us.html
If your cats absolutely cannot fly, perhaps crossing the pond by boat may be an option? This is what I am currently trying to coordinate:
Transatlantic travel by ship - with pets?
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There are several threads about moving cats and other pets - have a bit of a search, you'll find reassurance reading other people's stories.
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I hope you can bring cats with you - having your friends around makes settling into your new home so much easier. I would have been lost here without the muttley crew.
All the best.