This is a concern and like this family, neighbors and relatives had cared for the dog when the family vacationed before but now the situation is different and there is no one to care for their dog in the home.
For this season, I recommended a pet sitter to keep the dog as stress-free as possible.
After the holiday, I recommended that they begin visiting a kennel, walking around and having kennel staff give treats. After a few visits, when the dog is familiar and happily entering the kennel office, I recommended leaving the dog for bathing and grooming. This will help the dog understand that being left (in a familiar environment) will result in the owner's return. If this goes smoothly, they can try an overnight stay and be available in case the staff notices stress, and if this goes well, then a short vacation.
Personally, I think everyone should work to accustom their dogs to a kennel. Even if you have friends, relatives and neighbors that watch your dog, you never know when you might need a kennel. You want your dog to be comfortable in any situation when you are away.
Once you have provided your dog with a comfortable introduction to a kennel, be sure to use the kennel for a bath or overnight stay about every three months to maintain familiarity.