If you want to guarantee seats in the Valpo section and support the school a little bit (they have to sell a certain number of packages), get them through the school.
If you don't want all the games, or don't care as much about where you sit, just get an individual session ticket from the box office (there will be other deals on Ticketmaster through through the MVC as well) or Stubhub or a scalper.
I've done it both ways. Through the school when I knew I wanted to go to 3 or 4 sessions and could sell my Sunday ticket to a Wichita fan, and a one off when I couldn't make it down to STL for the whole thing.
You won't know until next year where the seats will be, but here's a recent chart to give you an idea.