You can add an action to the final page actionList and open explorer with the "explorer command"
<finalPageActionList>
...
<runProgram>
<progressText>Show logs</progressText>
<program>explorer</program>
<programArguments>/path/to/logs</programArguments>
</runProgram>
...
</finalPageActionList>
The finalPageActionList shows the users a set of actions they can choose to execute at the end of the installation.