Only the person who bought the tickets has the claim, so if that's you, then you're the plaintiff. You can't be represented by a lawyer in small Claims court, but you can have an interpreter.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
The proper person to sue is the person who paid for the trip. Also, you probably want to try writing a letter to demand your money back, as that may work quicker than a suit. Also try talking to other people at the travel agency. You may have your son come as a witness.
This response is general information and is not a complete review. This answer does not form an attorney client relationship. Please have an attorney review all documents before deciding on a course of action.