I actually ordered some on Saturday for this very reason.
It usually takes about three working days (sometimes longer if they have run out). They will email you when they are ready. All you have to do is go into my Rewards & then Collect Rewards (there will be a link in the email).
The only thing is that you don't get anything that you can really print off - you get a serial number & the top up code.
For a gift, what I normally do is just open a Word document & put €20 o2 Speakeasy Top-up, & underneath copy & paste the code from the Pigsback site, enlarge the font, put a space after every four digits, print it off & cut it to size & cellotape it to a christmas card. You could be a bit more creative, but most teenagers aren't that fussy once they get the top-up!