It depends. Can you provide transportaion and be available to present your show? How long is the show your planning to preform? What tricks are you planning to preform? Have read/watched anything about preforming for kid's? Have you practiced all of your trick's or the whole show adequtely? Do you think that you can handle kid's in this age group? Can you appropriatly handle anything that should go wrong i.e. misbehaving kids, a messed up trick, etc. I am not trying to discourage you and I wish you the best of luck but these are all important things. If your honest awnser to this is yes then I should think your on your way to being able to preform.
Thats whats happening right now I dont see myself doing birthday parties for atleast another 3-6 months because I need to practice and get some good kid tricks.
What do you prefer for kids tricks, does the pb&J illusion get good reactions?
Oh and for transportation I would just start out doing parties in my neighborhood, then move to bigger when I get a car and get a hang of it.