You really should. The first three might take a little "push" to get through, since Harry is still more like a kid than a mature teen. There is plenty of violence, but its contained in smaller bits and mostly to the end of those books from what I recall. The last three are likely to have you buried in them wanting to do nothing but read and break for food (well, that was me, anyway
) Goblet of Fire (book 4) really gets you ready and "bridges" the first and last three, preparing you with the increased length and maturing content.