Rules are rules. There is no point about the parents lamenting on the cops after commiting stupid acts like forgetting to take visa for kids and even forgetting to take PIO cards. These are caused by we indians being over confident about ourself and having the 'chalta hai' attidute and 'kam ho jayega' attidude.
Get your documents correct first. There is no point of complaining about immigration officials, i have always got good service, both at mumbai and delhi.