I completely agree about boarding your dog at a kennel. You can find many many great kennels that offer all levels of service.
I know that my family would be having a literal kitten if something was going on with our dog like this. It looks like you are at the mercy of this family flakiness.
Imagine this for a moment. My wife just told me there was a lost dog ad in the classifieds where the person left their dogs with a friend who dropped the dogs at the pound a few days before her return. The dogs were adopted out and she was trying desperately to locate them.
If you were to leave your dogs in the future with anyone then you need to have a hard contingency plan like a kennel that they can be dropped off at in case of emergency.
We did leave a plan — call us. My husband would come home. Or we’d arrange for her to go to our vet’s. We left cell and vet numbers.
Amen...done that many time with my local vet...while the dog was sad, no other difficulties were ever noted.