Before you do this there is actually safe different thinking about why you are doing it. It is not actually safer, and in some cases can be more harmful. What you are doing is giving an outdoor soft area, when most of the rest of the world is not soft. When the kids play, especially if they ar small, there is less energy to absorb so they learn that falling off stuff is dangerous and can hurt, but not too bad. If it is not risky then they can take bigger risks ( higher climb/jump/fall) and the risks are bigger I am not saying that you deliberately hurt your kids, but that they learn to play and they also learn what risk is. If they do not do this then then fail to learn about a key lesson: falling off stuff can hurt. If it is grass then it hurts more sometimes than others, if it is dry or wet, etc.
Grass is also self mending, looks good and generally not a place where cats/foxes/rodents want to poo and live. It also costs less as well. Just a thought.