For optimal holiday pleasure:
The entire family (including dog).
Pet passport with chip number.
First aid kit .
Telephone number of your own veterinarian and the nearest local (tip: keep in the first aid kit and in the telephones).
Water for the road. In countries where the water quality is not suitable for consumers, it may also be that it is not suitable for dogs. Then provide extra bottled water.
Harness (or collar) with medal with your telephone number, a spare copy and a medal with the details of your holiday address.
Line and reserve line. Keep in mind that your holiday address may have fewer run-off spots or there may be a lot of game. With a long line and well-fitting harness you can still give your dog some freedom of movement.
Own basket or blanket. A familiar scent makes the dog feel much more at ease.
Extra blanket (s) to protect the car and furniture at the holiday address.
Bottom pin with a strong line for the campers (of course do not record the dog without supervision). Check the strength of the line and musketone well. My experience is that these can (unfortunately) leave something to be desired.
Toys and chew bones. Ideal if you want to eat something somewhere. The dog equivalent of colored pencils for children.
Flashlight! Handy for a final pee in a dark forest; a lamp for your head is also very handy.
Depending on the country where the journey (goes through): muzzle, seat belt for dogs, car kennel.