You want to show it as a "bonafide gift" - "not for resale" - with a "value for Customs purposes only of not more than 20" If you are thinking to insure it - i would say do not - you will never collect on it, and it will only result in your son having to pay duty or VAT taxes on it. You need a "Customs Invoice" both on the outside in an envelope and on the inside. It is more expensive - but you are much better off using UPS, FedEx or another international courier - they do all the customs clearance and deliver to the door and it is automatically insured for about 100 USD.
I have some experience in this as i have been in international trade for almost 30 years.