Leave instructions and a day in the life type of outline, but nothing crazy. Mostly about bathroom breaks, exercise, food.
Dos and don'ts, keeping in mind it's their house, so he they may find it easier to let him on beds and furniture if the other dogs are on beds and furniture.
List any quirks and if they are unpleasant, how best to avoid them. Including health stuff, like if he eats a certain food he gets gassy.
List allergies and any other health information. If they can take him to your vet, call your vet and have them note that and place it in your file.
If you have a health insurance, make sure they have that information.
I left my emergency credit card with my best friend who I knew would be around and who always answers her phone and texts.
Bring a bed, bowls, leash, collar including a training collar if you use one for walks and pre-measured food. Extra food, just in case (a fresh unopened smaller bag).
On Rover.com you should note a trend in fees for dog-sitting for your area. For me it is $25-30 per night.