Please consider a licensed, bonded, recommended petsitter. My cat would litterally curl up and die if I boarded her. However, the petsitter we hired came once a day, cleaned the litter, refilled the water, and put out new wet and dry food (refilled the dry) every day AND left us a voice message on our telephone (we can call and get voice messages) telling us every day that she hadn't seen Sabrina the Cat but that the food was gone, the litter had been used, and everything seemed to be OK. She did this as a way for us to know that she had been there. It was her suggestion, not ours.
She was the best petsitter we've had. Our vet recommended her to us. That might be an option for you that might not be as traumatic on your cats AND won't cost you vaccinations (kennel cough and up to date shots) for your kitties before you can even put them there for your vacation.
Good luck and have fun!