I wouldn't bring up possible "diagnosis" until after the evaluation. There are so many things that can cause aspie behaviors. I did let my dd know that she was going to a "thinking specialist' because we knew that she loved to learn and we wanted to do whatever we needed to so so that she could learn even more - she was 6. Later, we started referring to the experience as her "brain test." It worked for us. DD remembers the testing as a positive experience.
The beginning of the Mysterious Benedict Society describes some kids taking a special, IQ, multiple intelligences test. Its a good read... All the kids in the book are special somehow.
