A - Thanks for the question and the compliments. The Catechism speaks with real authority, while the culture speaks with none. So, always go with authority.
In this instance, what has happened is that in common parlance, we sometimes refer to a child (or a deceased person we love) as an "angel". You have probably heard someone say that there is another "angel in heaven" after someone dies. This is just not theologically accurate. They may be saints in heaven, but not angels.
They are most likely just making a comment that they believe the person is looking down with love upon them and don't really believe they are angels, at least I hope they don't.
Angels are just what the catechism has said - pure spiritual creatures. Animals are physical creatures that do not have eternal souls (at least not like ours). Humans are the only creatures made with both an eternal soul and a body. We are incomplete without both. So, when we die our souls go either to heaven, hell, or purgatory (then heaven). Regardless of our eternal home (either heaven or hell), we will one day be joined to our glorified bodies after Jesus comes again. So, until that time we are in a sense incomplete.
Angels do not have the limitation of a body. Why are bodies limitations? Because they must dwell in space and time - at least on this earth. Spirits do not have such limitations.
There are other images that are inaccurate, these include chubby babies with wings.
Here are a few other facts about angels:
- They are creatures with much better intellects than humans.
- They are an object of God's love.
- They have free will and all angels serve God or are damned.
- They sometimes take bodily form (many stories in Scripture) in order to fulfill their mission as messengers to earth.
For more on angels, I highly recommend Peter Kreeft's book - Angels and Demons: What do We Really Know About Them?
I hope this helps.