I see you won't get to go on the Harajuku tour. Harajuku is actually fairly simple to get around if you want to shop. It also depends on what you're looking for, since Harajuku is the center of Japanese street fashion.
This map that Omotesando Hills provides is a simple representation of the area.
I usually get off at Harajuku Station, walk down Takesh ita Dori, make a right onto Meiji St and check out Laforet, and then walk back to Harajuku station by making a right on Omotesando St to head back to the station, but if you want to check out Omotesando Hills and more high fashion, take a left.
This is assuming you want to brave the trains.
I also only mentioned the JR Yamanote line, Harajuku station. You'll notice other stations mentioned on the map, but I'm not sure if you'd want to try understand the Tokyo Metro subway stations, too.