hi helen,
we have a very strict policy about the ticket holder travelling to ibiza with ID.
especially for busy parties such as avicii, the door staff (rightly) are very strict about this policy in order to get everyone in as quickly as possible. the only thing i can suggest is to cancel and refund the tickets (you can do this yourself through "my ibiza" - link on your email confirmation or at the top of any page in spotlight) and either pay using paypal and your own name or use your own credit card.
you can try to get tickets here, but it is a sell out every weekend, so if you do look for tickets here, make sure you get them as early as possible.
cheers