Chabad is not a secret society with secret meetings and secret plans..
Everything that we do should be based of the Rebbes teaching (Sichos, Igros and Maamarim) which are widely available in a number of languages. That is Chabad.
We have Lag Baomer parades NOT to convert anyone, that is ridiculous. It's to promote Torah, Mitzvos and Achdus among Jewish children, whoever they may be.
As for learning Chassidus we believe that it is important to a. increase in Yiras Shomayim, b. prepare for Moshiach (Amosai Ko'osi Mar..). This is something we believe that is worthy for all Yidden, not just Chabadniks, but we certainly are not trying to make everyone "Chabadniks". I don't know of anyone on such a mission and it is definitely not what the Rebbe stood for.
The reason why we learn Tanya, is because we believe that is a greater revelation (in depth and breadth) of Penimiyus Hatorah to the average person than the Chassidus that came before it. And that is why there was more Hisnagdus to the Alter Rebbe. The Noam Elimelech himself proclaimed about the Tanya "a G-d so big into such a little book!".