You can access Anna Maria Island 3 different ways: 

Manatee Avenue / Highway 64 which runs into the heart of downtown Bradenton (famous for the Tropicana Orange Juice giant – this is their main production plant and headquarters).  Other than that you could blow thru this town in about 5 minutes.  This road runs East to West.

 Cortez Avenue which runs into the lower part of Bradenton and is the route you want to take to get to Sarasota.  It runs exactly parallel to Manatee but does not go as far as I-75.  You can jump between Manatee and Cortez on a number of streets, but look at a street map before you take one.  Many are dead end streets or twisty roads that wind in and out. 

Longboat Key Bridge which is on the Southern tip of the Island and connects Anna Maria Island to Longboat Key Island.  You would only go this way if you were sight seeing on Longboat Key or going to St. Armand’s Circle or taking the long way to Sarasota. 

Once you are on the Island, simply head North on Gulf Drive.  This is the only road that runs down the middle of the Island.  Note that the Island consists of three (3) small towns or cities.  The Southern part of the Island is known as Bradenton Beach and has surf / beach shops, apartments and resembles the Jersey shore.  The Middle part of the Island is called Holmes Beach and consists more of condominiums and timeshares with some residential.  The Upper or Northern part of the Island is called Anna Maria and is mostly residential, no tall buildings (nothing over 3 stories is allowed).  No condominiums, not even mail boxes are allowed.  It is the snooty end of the Island, but I like it just the same.   

As you go North on Gulf Drive you will pass thru Holmes Beach and continue North until you come to Magnolia Avenue.  Simply turn right and go 1 ½ blocks and the house is located on your left surrounded by trees.

Here is an overview of the route from Long Boat Key to the Beach House.

Watch for the Beach House on the "left" surrounded by trees with a "coral" (pink) driveway.