Have if I understand you. Osea you you keep your same team, just that your chip is what your father went through and some vice versa?
If so, then you have two ways to change your number Whatsapp.
1-You go to Settings WA
2-Click Account
3-Click on Change number and then follow the steps indicated by you
The other would be:
1. You take a backup of your entire conversation Settings / Chats and calls / Chat backup
2. Then place yourself the file in the WhatsApp / Databases folder and select the latest copies you made and the micro SD or PC
3. Then in the Application Manager, the Whatsapp place yourself and give click to clear all
4. From there you return to put the backup folder where extraiste
5. You open the application and go back to now put your new number
6. You ask and you are restoring data
The first option is the right, but try to have the chip now your father without active use while yours, otherwise you can cross the numbers, as the number you have still enabled in your father Whatsapp.