You should never put rat poison down, its not safe for kids..it will kill them if ingested because by the time you see the symptoms its too late there systems will start to shut down.
It doesn't matter where you place the rat poison, down a long pipe etc, a rat will always take food back to its nest, this is a know fact, so if he drops it along the way, then your leaving yourself very exposed to a potiental death.
If you have a problem, get a pest company in to assess the situation and to give you solutions especially when you have kids. There must be a reason for having rats in your garden..and they will assess this..
I personally think this thread should be closed as any advice except from a professional should be disregarded especially when you have young kids..