Hi Chrissy,
Can you borrow a friend's dog for the weekend. Once they realize a dog has come to town, the property will look MUCH less appealing. You would have to do this repeatedly to make it work.
If you have a sprinkler system, turn it on next time they are in the yard.Or you can just use a hose and spray them when you see them. They won't want to come to a place that sprays them. Cat's tend to freak out when they get soaked!
There are also various sonic devices that may or may not work. And they can be expensive!
Grow a garden of plants that are repulsive to cats. Plant peppermint, geranium, rue, lavender, garlic, lemon grass and thyme along the perimeter of your buildings to keep cats from entering.
Alter the comfort zone by making your property 'unattractive' to the cats! Spraying the area where they rest with the following may help. Citronella oil works well, as well as citrus scents such as orange or lemon, cayenne pepper, lavender oil, lemon grass oil, peppermint oil, eucalyptus oil, and mustard oil. Spray hot pepper formula around the flowers and on top of the mulched areas. Or get a 2lb bag of fine ground pepper and sprinkled it liberally around the areas the cats visit.Try coffee grounds or pipe tobacco. "Havahart's Cat Repellent" uses capsaicin pepper and oil of mustard as its active ingredients. It repels by both taste and odor, has a lemon scent.
Every cat responds differently to each of these. Some will not be phased by them and others will not.
By the way Chrissy, I happen to love cats, just don't beleive they should be allowed to roam!