The wording they use is "all original documents used in your application". So basically if you photocopied and mailed it, you now need to bring the original with you to the interview.
Did my test yesterday. While I was prepared for the worst, it went really good. They asked my wife to sign on the paper that she has filed the taxes. I was expecting a RQ due to my extensive travel but she said she was able to verify all the dates are correct and I had a big buffer ( Approx 250 days). Test passed with 19/20 for me and 20/20 for my wife. Now just have to wait for the OATH
You don't actually need to take anything relating to child/children. We had our test this morning, and i took our child's paperwork too, but she said we didn't need to and she didn't look at anything relating to the child's paperwork.