A year or so ago, my DS had $300 Disney $'s he received as a gift that he couldn't spend (13 year old!). He took it to City Hall and they exchanged it for cash, no questions asked.
I don't think you even need the receipt, just the DD. We did it but it was years ago. If DD doesn't spend hers by this Dec tho we may have her trade it in, since we aren't sure we will renew our APs......