Is there any way to use one Whatsapp account in multiple device or is there any tracking system in whatsapp? I want to use one Whatsapp account for multiple devices. Actually I have two kids and I want them and my wife to use same whatsapp account in order to keep a track of their chat. I am also ready to give them separate phone numbers/accounts but I should be able to use their accounts in my device along with my own account. Is there any way to use one Whatsapp account in multiple device or is there any tracking system in whatsapp to keep track (chat history) of other numbers in one device?
You can use WhatsApp web on other devices. It is the secure way but the active internet connection on primary phone is necessary.

Please make sure you visit desktop site on the phone to use WhatsApp web. More details can be found here on Quora.