Of these three options, the second would probably be the most efficient for you and our trademark team. The current trademark enforcement policy allows for the trademark holder to authorize use of their trademark terms in specific accounts via a letter on their letterhead faxed to Google. As long as the letter you give your retailers has their AdWords account number in it, or a place to add the number to the form letter, it should suffice.
And just to be clear, registering your trademark with us does not prevent competitors, or retailers, from bidding on the term. It only prevents them from using the term in their ad text.