When I went to Disneyworld last year I had a total of 17 cats in the house, one of whom was diabetic. They were in different parts of the house; I had the pet sitter (another rescuer) over a few times to meet the cats, give Moby her insulin, feed and clean, and generally find out where things are. So that's a perspective from someone with a load of cats (although not 23!)

I gave her a list of all the vet #s, and opened an account at each to authorize any needed care. (I didn't need it, fortunately, but with an aging diabetic you never know.)

Being able to get in contact with the petsitter is very useful, just as a safety net to ask questions.