The gang of neighborhood cats have decided that my vegetable garden plot is
the place to crap in.
What can I do to put a stop to this?
I have a dog, and young children around.

If these are feral cats, speak to your local animal control warden. If they
have owners, remind the owners that their cats will be safer & healthier if
they are kept indoors.
Keep your dog and children out in the yard as much as possible. It is healthier
for them anyway.
There is a motion sensor sprinkler you can get to attach to the hose, which
will chase them away harmlessly. There are non-toxic repellants you can get in
the pet store. They need to be applied after every rain.
If these cats are so fearless they come around when you are there, a water
pistol loaded with ammonia solution will act as a deterrent without doing any
serious harm.
Consider using plastic mulch after you set out the vegetable plants.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)