SSH from different Wifi network?
Firstly ask your parents to turn on your iPad and connect it to the local network.
If you have remote administration on your router you'll be able to do the next steps yourself, else you'll need your parents to do it.


Login to your router's administration page
Get the external IP address of your router (if you can set up dynDNS this will make your life easier in the future)
Work out the IP address of your iPad
If your router allows you to, it'd be useful to assign it with a static IP address
Navigate to the port forwarding page (probably under security or firewall)
Configure port 22 (standard for ssh) to forward to your iPad (some routers will allow you to forward it to a MAC address making it doesn't matter if the devices IP address changes)
Now, from your computer SSH to the external IP of your router (or dynDNS address if you have that)