According to the Catholic Church, what was the point of all the plagues?

Did God really have to do all those plagues in order to get Moses' people free? Did each plague have a particular purpose? I heard about a documentary or hypothesis that only first or first few plagues were intended and then the remaining plagues, except the last one, just occurred naturally. Even if we grant that all but the last plague were purposeful or natural, what was the point of killing innocent children, particularly the Pharaoh's son? Why not kill the Pharaoh and then have the son or regent rule and then have the next ruler of Egypt set Moses' people free? Why not send a bunch of angels to threaten the Pharaoh into releasing the Israelites or into offering fair wages? I doubt this is relevant to the problem of evil as God specifically intervenes in human affairs in Egypt. Why all the violence though? It seems to make sense that an omnipotent, omniscient, all-good being who would intervene in human affairs would want to do so with little bloodshed unless there's a specific lesson that the being wants to impart on the Egyptians or Israelites or something of the sort. Maybe the Israelites wouldn't have appreciated God's efforts as much if it was that simple? Also, I seem to recall from high school something about wanting to convert the Egyptians. What does the Catholic Church say about this?