Volume EQ suggestion

Hi everyone. I hope I am in the right place to share my suggestion. But is there anyway we can get Apple to add a master EQ. My son has discover the volume button on his iPad. I am constantly turning it down. The apps he play on does not have any configuration for volume beside on/off. With this master EQ idea, say it's set at 50% voulme, when he turns it on max with the button it still play be at true 50%. Also a password protect to the "setting" be nice too.

If this already exist and I miss it please show me. Thanks.