More odor-control suggestions please

My aunt is kind to the strays but not enough to adopt or care for them. She lives right beside the ocean and so the ground of her small yard is mostly sand. It's also the strays bathroom.
Last week while visiting my mom she complained to me of the odor and because she will never harm the cats, she asked me what else can be done to remove the smell. I suggested she powder the area with baking soda, and sweep away the cat poo she can see or bury it deeper.
What else do you recommend?
I know cats won't poo near their food and since my aunt feeds the strays, should I tell her to start leaving the food in her yard so the strays can do their business elsewhere?
Thanks.
PS: I did recommend TNR.

I know someone on here had a suggestion for keeping strays from using the garden as a litter box... I believe it involved a type of used tea bag and some kind of natural oil - whoever had suggested this is, please speak up! My mom needs the remedy as well.... we've got a stray that's now had two litters in our area - the mom is real nasty and no one has been able to humanely get them (except the runt from the first litter that my mom took to a shelter - she's allergic to cats and we didn't know anyone who would take the little thing) and they're using gardens to poo in.... I'm thinking the same remedy will work for this sand situation

Leaving lemon or orange rinds around might work, but maybe the solution is worse than the problem...

At home I use vinegar to remove the smell, and leave it for a while before washing it up. I don't know if this will work outsides though...

Thank you for your replies!
I did think of recommending "lemon rinds, used tea bags, etc." but those might attract other small animals to her yard. My aunt does not mind the kitties going to her garden, but the smell of the "souvenirs" is becoming unbearable.