2-If you've got the tricks down, what does it matter how long you've been doing magic. What difference is it if someone masters a trick in 5 years, or in a day? Of corse I don't do a trick once and say that I've mastered it, I practice all the tim.
Surprisingly enough, when performing for kids, there are a few things that are more important than actually mastering the trick. You'll need stage presence and crowd control. There isn't much skill in doing a cut and restored rope, a vanishing silk, a coloring book etc. But how you do it counts for a lot. For kids, you'll be more of an entertainer, than a magician (a david blaine approach doesn't work for kids parties). Read up on David Kaye for some ideas. Take notes, plenty of them. Most of what he says is gold and was a great value for me. If you are serious, look up the book "the birthday party business" too.
My best tip for you at the moment, is get experience with kids. Who cares about your actual magic skills. Plenty of good magicians don't know how to to magic for kids. Volunteer at a daycare or something in this style where you will be in charge of a group of children. Performing for family and friends isn't the same thing as performing for strangers, especially group of strangers. This is the best way to learn a lot about crowd control and all of that mumbo jumbo. Then if that's a piece a cake, consider parties.
And for the shyness, well I guess it's experience. One thing that might help is creating a character. A character that isn't shy would be a start.
I don't want to discourage you, but there are also other things to take in consideration when performing for strangers, like legal things and all that fuss. Reading up on this sort of work will tell you all about it. So for the meanwhile, it's maybe safer to stick to friends and family. If you truly want to do this, take it seriously. Slow down, there is no rush. Remember this is an art, only expose it when you are absolutely certain you are ready for anything that might happen.
Hope this helps, good luck. Feel free to contact me for any other advice.