They had a battle station, they wanted to test a battle station, they just lost the plans to the battle station when an escape pod went down to Tatooine (note there is only one "n" in Tatooine, and it's after both "t"s). Tatooine wasn't significant. Forget Alderaan - just blow up Tatooine.

Your statement that it was important is contradicted by everything said in the movies:

1. In Phantom Menace, they say it was a minor, unimportant planet on the Outer Rim that consisted mostly of moisture farmers and controlled by the Hutts - a group neither the Republic nor the Empire particularly liked.

2. In the original Star Wars, Luke says "If there's a bright center to the universe, you're on the planet it's farthest from" and repeatedly calls it a "rock". Its chief city is described with the words "Never will you find a more wretched hive of scum and villainy."

3. If you're ignoring the injunction not to talk about the Expanded Universe, then I might as well point out that (a) Tatooine is not in Hutt Space and would not have been a major planet owned by the Hutts, (b) it had only 2,000,000 inhabitants and so was sparsely populated and (c) the planet had no valuable resources to mine.

As for the novels you're talking about, it's about time somebody killed Chewbacca. I mean, what's a Wookie doing on a planet full of Ewoks?