@Richard1387 Tons of hosts have this situation, and to be honest, it's a lot better idea than renting out a place where you don't live. You can keep an eye on things, it pretty much kiboshes partiers or trying to sneak in extra guests, and you're readily available should the guests need assistance with anything.
Yes, you definitely need to mention it in your ad, but do it as a positive- "As we live in our separate house on the property, we're always available to answer any questions or assist you if you need help with anything."
You'll become adept after awhile at picking up on whether guests just want to be left alone, or if they would enjoy being invited to join you for a backyard barbeque or a game of catch. Those kind of experiences, for guests who are so inclined (assuming you're up for that occasionally as well), can lead to great reviews and repeat guests.