We are indeed planning to travel. (Overseas. Extensively.)
If there was a way we could take our cats with us, we absolutely would. Our plan though is to live in a place for 1-3 months, then move to the next country, live there for a bit, and then move on, and so on and so forth. We plan to travel the world for years.
What that means for the cats is that they'd go with us, be stuck in quarantine (most places up to four months). By the time we got them and were moving on (and forced to move on due to visa issues), we'd only have them for a short time, at most, if we even got them at all (they didn't just ship to the next country). They'd be stuck, alone and scared, in quarantine, for long stretches, over and over.
That's no thing to do to animals.
Our other option is that we keep them. We don't live our dream of traveling the world, and just stay here in the US for the next decade until they both die. That is an option we're considering, just because we do love them. But it is also not ideal, as traveling is our main ER goal, and without it there's not much point of ER for us. So our considering it is us saying "I guess we can just keep working." But continuing to work a decade+ past FI just for the cats also seems a bit silly.
So we're looking into trying to find out how we can find a wonderful new home for them. It's not what I want to do, but it may be the best of the various options. If it comes down to it, we'll pay whatever price that entails to make sure they are well cared for. I have mostly avoided this thread after the initial day of creation, as dealing with this has been very hard for me. It's hard for me to visit the websites and read about the options without getting emotional. It's something we're looking into now, way ahead of time (6+ months), to make sure we can find something that we feel comfortable with for them. If we don't find something, we won't be leaving.
Thank you everyone for your suggestions.
I realize that people will disagree with what we are doing, and that's okay. You're more than entitled to your opinion that I'm a scumbag. Sitting here next to my sleeping cats, I'm not sure I disagree with you.