I have a 48" zero-turn, gas powered. No goose poop in the treads. We have thick St. Augustine grass that I cut at 3.5". I guess the goose poop just disappears into the grass and becomes fertilizer. It's never been the slightest problem. We like the geese... and the ducks and herons. They are fun to watch and observe their behavior. It's part of the appeal of living on a waterfront lot.
Regarding border collies, ours is 10 years old now. So he's calmed down a lot. But he was a neurotic-like mess until a couple years ago. Very unpredictable. Non-social. Occasionally dangerous to strangers. They are hard workers and very loyal. But you have to have the time to "work" them constantly. They want to work and they want to please you. But, without a herd of sheep, modern humans don't have that kind of time or patience. So the dogs vent their frustration with neurotic-like behavior.
He was 2-3 years old when we adopted him. I had just retired at the time, so plenty of time to work with him. But still... OMG... a very unpredictable dog. Don't get the wrong idea... he's sweet and lovable. But if you do something unexpected, like dance to a Stevie Wonder song in the kitchen, he will snap at your face and try to get you to behave and "rejoin the herd."
So yeah... be careful with this breed. No doubt they will keep your geese away. But they might also keep your grandkids away. And that's not good. We have to crate him when the grandkids visit. Even as a 10-year-old dog, he's still frustratingly unpredictable.