We self cater 4 or 5 times a year with and without our dog. Things that are important to us which are sometimes forgotten:
On the website: lots of clear pictures of the interior and preferably a floorplan like the Landmark Trust do. No arty photos of pebbles or door knockers 
A bright outside light so you can find a strange keyhole easily!
A bread bin (just come back from somewhere without one) and board
Lots of crockery and cutlery - enough to fill the dishwasher and still have plenty to use (and big mugs not just teeny ones)
Glasses which are nice but not too delicate otherwise people like DH will smash them!
Simple instructions for everything rather than the manuals
No notices up - my pet hate is staying somewhere with notices everywhere you look. Just have the 'rules' in the property's manual
Milk, teabags, coffee, a loaf, jam and butter is perfect. If there's a cake and a bottle of something, even better
A keysafe. I prefer not to be shown round by the owner, that puts us under pressure to be there for a certain time, and its much more exciting discovering the home on your own
Lots of coasters
Absolutely no crinkly plasticky/rubber mattress covers. That puts me right off . The cover needs to be something that doesnt make you feel sweaty
Same for pillows
No fabric or leather headboard
A hoover somewhere handy so we can whizz it round as needed
Nightlights for the landings, plus a torch to take out in the evenings
Some of those shoe/boot trays at the door so you can put your muddy boots straight in them
Re dogs, I'd say that if they are allowed, the norm we've found is that they arent allowed to be left unattended, not on furniture and not upstairs. Where we have just come back from had lots of dog towels, dog treats and even a spare lead. They had tiled floors so really easy to clean too. Coquet Cottages do the dog thing really well here
PS more than happy to do a test run for you 