The Lantana plant can be toxic to dogs and humans if ingested in large enough amounts.
However if the dog or human such as a toddler or small child eats a leaf or takes a bite of the Lantana plant then nothing will happen to them.
Just don't let your dog or kid eat the Lantana plant when you see them about to eat them.
My brother took a bite of Lantana when he was 2 years old and he went to the doctor and they said it was of no harm to him as long as he didn't eat anymore of it.
You would basically have to sit down and eat an entire plate of Lantana before it became toxic enough to kill or really harm a child or dog.
Your dog or child would likely not take more than a few bites of the Lantana plant because the leaves are very rough and have a terrible fragrance that makes them unpleasant to eat much of it.