Feral Cat problems

Scarecrow Water Sprinkler by Con Tech

I've been battling stray cats for a couple years now. I'm tired of picking up their poop when I find a few minutes to work on the garden... as such, my veggie garden is still non existent and my front yard is unfinished. So this past year, I've been searching for solutions.

Last year, I just caught them all (about 30) and sent them to the humane society to deal with. I refuse to do the catch and release program as I don't have the time and money, but unfortunately a neighbor here confronted me when I started catching the strays this year. She and her family loves the kitties and would like me to leave them alone. She likes to feed them and has kitty food in her patio for them. I informed her about the program and asked her to look into it so the cats don't breed... less poop maybe. At this time, there are about 8-10 out there. And again, they're using my yard as a pooper. Most of the other neighbors I've spoken with don't like the situation either. We would prefer them gone, but out of respect for this family, we put up with the situation.

Because of allergies in our household, I do need them to stay out of my yard, so I've been on a quest to find an appropriate repellent. My oldest daughter (now in college) comes home and is constantly coughing and sneezing when she's downstairs with us. And my skin has been itching a lot again. I think it might be the cats as we've tried major housecleaning, changing soaps/detergents, and skin care lotions. We KNOW we're allergic to cats... so it's possible. Hopefully, when we can get them to stay away from our home, we'll be able to enjoy it again.

Here's what we've tried that hasn't worked:
Citrus peels (lemon, tangerine, orange)
coffee grounds
black landscaping plastic (they just ripped right through it and pooped)
egg shells
Big glass jar filled with water

Here's things we considered, but decided against due to little children who like running through our yard (hers as well as ours), or cost factor of having to replace it every time it gets wet.
Chicken wire around the plants
Thorny branches
Cat repellents

Here's what looks hopeful. We've been using these since Christmas and they seem helpful:
Pine branches from our Christmas tree (my alternative to thorny branches)
Scarecrow water sprinkler by Con Tech (expensive, but maybe worth it)

My Scarecrow was broken for a couple days, and I found cat poop on the lawn, right at the bottom of the kid's slide. That would've been unpleasant. Con Tech's customer service is excellent and the warranty is 2 years. The replacement piece came just 3 days after I emailed them. That's extremely quick for delivery to Hawaii. The only thing I don't like about the Scarecrow is that it also is spraying the birds. I like birds and don't mind them in my yard. Wish I could keep them visiting without the cats...

I'm planning on purchasing a few more of those Scarecrows, hopefully I'll be able to figure out a way to keep them safe from the children when they're running through my yard. And I'm going to see if I can hook up a system of these to my water sprinkler system.

Comments welcome on how you're dealing with feral cats.