For those interested in the topic, I solved my problem using the first solution, here is the ant target used:
<target name="build-javadoc">
<echo message="Creating Javadoc.." />
<delete dir="${doc.dir}" />
<javadoc access="public"
destdir="${doc.dir}"
sourcepath="${src.dir}"
docletpath="${doclet.dir}/doclava-1.0.6.jar"
classpath="lib:libs:/Users/myusername/android-sdks/platforms/android-17/android.jar"
packagenames="com.my.package">
<doclet name="com.google.doclava.Doclava">
<!-- Title -->
<param name="-hdf" />
<param name="project.name" />
<param name="Project Name" />
<!-- Overview -->
<param name="-overview" />
<param name="src/overview-summary.html" />
<!-- Template -->
<param name="-templatedir" />
<param name="Doc/My_Template" />
<!-- federation Java -->
<param name="-federate" />
<param name="JDK" />
<param name="http://download.oracle.com/javase/6/docs/api/index.html?" />
<param name="-federationxml" />
<param name="JDK" />
<param name="http://doclava.googlecode.com/svn/static/api/openjdk-6.xml" />
<!-- federation Android-->
<param name="-federate" />
<param name="android" />
<param name="http://d.android.com/reference" />
<param name="-federationxml" />
<param name="android" />
<param name="http://doclava.googlecode.com/svn/static/api/android-8.xml" />
</doclet>
</javadoc>
<echo message="...Done" />
</target>
Hope it can help someone