your hotel is listed as pet friendly do we need to let you know that we have a small dog before we book?

I would let them know just to be sure

I would let them know in case they use a specified floor

Definitely let them know in advance, almost every pet friendly hotel has a limited number of pet-friendly rooms, so you need to book those in advance. Many people are allergic to pets, so hotels have designated rooms for people with pets, and if those are booked you're out of luck.

Yes! It would be better to give them an advance call before arriving there.

Best to contact them directly and not just post on Google