chefdanny while everyone has very good points. I have to agree that you may not want to plant anything that would attract more deer. And while inviting friends to help take more deer is a sportsman like idea, I would exercise caution in doing this. First of all this coworker and his wife have invited you to hunt this property, rather than open it up to public hunting. This tells me that they probably don't want a army of hunters invading their 20 acres of paradise. Therefore before I would invite anyone else I would clear it with the land owner. Then if it is ok with them, be careful about who you invite. Make sure you let anyone you invite no what you expect. Whether or not they have an open invitation or are they allowed to hunt only when you are hunting. Whether they are allowed to invite anyone. I have seen friendships of many years come to an end because of miscommunication and squables over hunting property. I once knew a friend that allowed, what he thought was a close friend, to hunt a property that he had pemission to hunt. Only to have this so called friend lease this property out from under him 2 years later.
As far planting, if you are looking for an attractant I would go as far away from the property owners garden as you can get and plant something like Whitetail Institutes "No Plow" or "Secret Spot". These products are an annual fall planting food plot blend that work well in low light conditions. While I haven't used "Secret Spot" I have used "No Plow" with great success. In just a matter of weeks of planting it the deer had a trail a foot & a half wide and 2 to 3 inches deep leading to it. Again I would clear anything you do with the land owner.