A simple and practical way to connect to the web version of WhatApp with your iPad is using the app “Push Messenger for Chat App”.
Just like the web version of WhatsApp, the "Push Messenger for Chat App" is an extension of your phone, which simply mirror your conversations and messages as they are in your phone device, that means, all your messages remain originally saved on your phone .
To connect, open the "Push Messenger for Chat App" and you will see a QR code, simply scan this code using WhatsApp on your phone and you will be logged in. You will find this option within WhatsApp settings on your phone, at "WhatsApp Web" menu.