I'm so sorry you're going through such a hard time right now - what with grieving for your mother and worrying about her precious kitties.

I just have one question for you to consider -

Are they really a close, bonded pair of cats - or have they simply grown up together? (thinking of my own cats, our female wouldn't lose a night's sleep if the two boys vanished tomorrow and she became an only cat).

Sorry I don't have any more ideas - but if given the hard choice with the limited options - I would lean towards the option of each cat going to a separate home.