I don't think you'll need the passes on Thursdays or Fridays, but weekends are pretty crowded. That's been my experience thus far, and I've been able to get into every house. Just pay attention to where most of the crowd is, and avoid it if possible, and you'll be fine!
Note: I do go to Uni Orl, but the patterns of the public should be very similar between parks. I am not at all sure how the terror tram works, however, so I can't say anything about that :T