Hard-reboot your iPods, which can be achieved by holding down the power button and the home button together. Keep them held for roughly 10 seconds, and wait for your iPods to reboot. Once they have been turned on successfully, close any and all background task(s) (from the multitasking as you call it) and retry what I mentioned above.
If you are still having problems connecting too eachothers local world, then you might want to conisder checking (or getting your parents to check) your Wi-Fi restrictions. Make sure all necessary options for multiplayer (worldwide gaming) restrictions are turned either on or off.
NOTE: you may need to restart your router for changes to take affect.
Once again, relaunch Terraria, and try hosting and joining. If this problem still continues to occur, then I suggest you post this in the troubleshooting category, and explain clearly what is happening.
-Regards,
Nero