And this is where I plead to the world to wish -- VERY, VERY HARD -- that the WiiU can tunnel the 3DS online through an official means.
Give up.
Online tunneling would be a useful feature for those with a Wii U, a 3DS, and MonHun 3U for 3DS.
However, if you have all this, I'm quite sure what Capcom really wants you to do is to buy the Wii U version. The online component is the major selling point of 3U for Wii U. You want them to take that away?
Besides, it's far too late for them to add such a thing now. Just fucking wait for MH4 if you want a 3DS MonHun with online multiplayer so much.