I feel like 3 is too young to do any testing and wouldn't accomplish anything anyway. What about 4? 4.5? Is it too soon to start getting documentation so I can advocate for him?
Personally I feel that if you test when your child is young, you might find yourself questioning the results if they don't come back showing what you expect. You also may potentially find others will question the results due to age when you try to use the results to advocate, unless you are applying for a program that requests the specific testing.
OTOH, it's never too early to start documenting what *you* are seeing in your child. Keep a journal/record of the things you see your child do that appear to be advanced. If you find yourself in a position a few years down the road advocating for your child you can share what you've observed.
Best wishes,
polarbear
