Do you feel this is something that needs to be noted when you are initially making your estimate and walking the grounds?
Like if you see there are pets, do ask the customer if they can remove them on the day of mowing? So everyone is on the same page?
What about dog waste. If the yard seems to be covered in it and you see it, do you bring this to the attention of the customer and ask if they want you to pick that up as well? Then tell them a cost for that service?