Can’t keep cats-worry about them staying together and being alright

TLDR-moving and can’t keep my cats together. Will they be okay?

We adopted our (F3) youngest when she was a few weeks old and our grumpy guy (M6.5) a little over a year ago. F is very playful, polydactyl and loves to
run but hates being cuddles. M is the opposite, as he enjoys cuddling (so much he drools) and sleeps 24/7. Due to some unforeseen financial troubles, we have to give them in a few weeks while we go live with in-laws for about a year and a half, and they are very adamant that the cats cannot come. Unfortunately, we can’t afford to stay in our apartment. M has jumped around to a few homes before landing with us, but we’re all F has really known. M also has a health issue that causes him to stick to a special, slightly more expensive diet. We also have a dog that we got before both of the cats that we are taking with us. At this point, we don’t have friends or family to take them and can’t find any non-sketchy stranger to rehome them too. I know that this will end with giving them up to a shelter nearby (a no kill shelter, that’s clean and treats their animals well) but I’m worried about their mental health. Especially F, as she’s only known us and our dog. Do shelters actually honor keeping pairs together, and will they be okay?