Action sequences: cool but deadly!

Now when I was writing the Talking Cake, and another book I'll just call A girl's adventure, I noticed that writing action sequences is very hard. Especially when the action sequence's main characters are of kids ages 10-16. I noticed that I had either two choices: Try to make the most action filled sequence, or a action sequences which is very kid friendly. Here is the list of stuff I did wrong in A Girl's adventure
1. there was the fastest car on earth in it(it was a car chase). It is like super unrealistic and very cheesey
2. it went into big detail( ex: The car spun around in circles, and Lucy shot three bullets. She moaned and put more bullets into the gun). Now I know you probably won't think that is bad, but when you read the whole book(I might post a chapter onto the blog) it will show how bad it was
3. I had young teens( ages 18 and younger) participating in action sequences that you would never imagine a person doing in real life. 4 example: the youngest character which is Lucy ends up using guns
4. I definitely dramatised an action scene in the end of the book. Let me just say that use weapons from this year. For some reason that I don't remember they used swords, and medieval cannons in a book that took place in 2007.
5. I had young characters traveling around the world without an older person

I am ashamed of A Girl's adventure, though I always wanted to remake it. Make the characters older, cut out the cheesy dialogue, and and the obvious plot turns.
-AM