An ipad app or setting that helps turn off wifi or turn on airplane mode on schedule?
No. Not unless you jailbreak your device.

There is obviously Do-Not-Disturb which disables alerts, but does not put the phone on Airplane mode or disable wifi.

Keep in mind that if you turn off wifi, or enable Airplane mode, that iCloud backups or iTunes backups won't work at that point. 

So, in order to conserve battery overnight, you will need to manually enable Airplane mode, disable wifi, or, you could power the device off completely. Again, keep in mind, iCloud backups will not perform during this time.