I will need to know if the dog has any allergies, other physical health problems or ailments and how to accommodate them, and their general personality (for example if they like/dislike cars, water, playing catch, etc.)

I will first and foremost adhere to whatever instructions I have been given by the owner, including on where to go. But if allowed to make my own schedule, there's lots of fun things to do on a dog's day out! We'll walk around routes with plenty of shade to keep cool, away from busy traffic, and I'll be sure to bring enough water for both of us. If they're a fan of cars we can drive to any local park and play catch, maybe even hit up an ice cream shop that serves doggie ice cream. There's lots of options but it will generally depend on what the owners and the dog(s) want.