What is a safe decibel level for a kids game?

You mean the sound pressure level direct at the kids ear, because the level in decibel is dependent on the distanca from the sound source. Go as far as possible from the noise. Nearly "Safe" is a level of 60 dB SPL, but it makes nervous. Learn about decreasing of the Sound pressure. Scroll down to related links and look at "Sound pressure and the inverse distance law 1/r".