I will use your suggestions and find them a nice retirement home... If anything bad happens to them, I just dont want to know...
That's why you do have to find them a caring place to take care of them if you never intend to bring them over; not send them away and then close your ears and eyes. I'd think that would inevitably wreak havoc on your conscience.
I left my cat behind because I didn't know what my situation would be initially; with the intention of bringing him over once I'd settled. My parents took him in, even after years of saying they couldn't take care of any more animals (my whole life, animals have found us, never the other way around); and eventually, they had to be the ones to take him through being put down (of old age/kidney failure in 2005; he was 14 when I left in 2004).
I don't know what I could have done differently, but I will always feel guilty for putting him and them through that; as I should have been there. I miss him horribly and can barely bring myself to even begin to grieve.