Account Limited: Cannot complete the required steps!!

Hey..my account got limited..
have already completed two steps,they are:
-Adding credit card
-More information about payments (All details have been submitted here)
I am working on completing the steps i can.. like the photo id and proof of address... but there are two more conditions:
-Provide invoices
-Proof of delivery

Since the money in the account is earned by my son, who is underage and cannot have his own account, by freelancing (Coding and designing) he just deals with digital files... so we don't have any merchandise or any bills or the lists of goods in that regard and thus cant provide with the bills of sale or lists of goods etc..

Also he sends the files by either Uploading to the clients server/email/IM so we dont have any proof of delivery...

Please help..What should i do??