[What did the store need to incur attorney fees for. Criminal prosecution is handled by governmental-employed attorneys, not by the victims such as the store.
The store is suing you for their attorney's fees? There is a statute in Wisconsin which makes the parent liable for the attorney's fees, but I think this would be for a civil case, not a criminal one.
"895.035(4)
(4) Except for recovery under sub. (4a) or for retail theft under s. 943.51, the maximum recovery under this section from any parent or parents may not exceed $5,000 for damages resulting from any one act of a juvenile in addition to taxable costs and disbursements and reasonable attorney fees, as determined by the court. If 2 or more juveniles in the custody of the same parent or parents commit the same act the total recovery under this section may not exceed $5,000, in addition to taxable costs and disbursements. The maximum recovery from any parent or parents for retail theft by their minor child is established under s. 943.51."
So, no, in my opinion, you aren't liable, although your son might be. But the argument you are making, that he was tried as an adult therefore his parents aren't liable for damages caused by misconduct of a minor, doesn't hold water in my opinion.