Tethering doesn't really add more data usage unless you are trying to use it to replace a home internet connection (in other words downloading movies, pc games, etc.) If you don't try to do those things, tethering won't add much to your data usage.
However I don't find 2GB appropriate. I am only downloading an app or two a day, averaging under 10 mins a day of youtube, and doing basic internet browsing stuff and I am on pace to go over 2GB on my first month. Now I didn't use any wifi during that time just to get an idea how fast I use data. If I always use wifi at home I should make it alright, but that is because I spend a lot of time at home.
If you have wifi at home, it will probably be enough. Just be careful how much you want to use pandora, as it will eat up those 2GB with ease. Remember, it isn't a 2GB only plan. It is still unlimited, it just isn't flat rate. So if you go over 2GB, then it's $35 instead of $25 and you get 3GB which should be plenty. Even if you went over 2GB every other month, your data charge would average out to the same as the unlimited plan. It is unlikely to go over 2GB that often.