Just copied this from Apple's support page on iCloud backup.
You can select which applications back up their data and see how much storage space each application is using:
On your Home Screen, tap Settings
Tap iCloud
Tap Storage & Backup
Tap Manage Storage
Select the device you want to manage
Since I don't have Hay Day, I am guessing, but if you are using iCloud for backup, I assume you should make sure that Hay Day is in the list of apps that back up to iCloud.
But...as recent events have shown, doing a local backup is of paramount importance. Then if your iPad craps out, you can do a restore and be back in business without a break. Don't take chances with your data. Neither Apple nor the game developer are responsible for it. It's your data. Protect it.