ADOS Test and diagnosis

hi, i am fairly new to this site and this is my first post.  i have a 3 1/2 year old who since birth has displayed unusual behaviour/querks.  he intitally was referred to a SaLT and a speech group. whilst at this group they noticed how he behaved.  i reported on his behaviours at home to.  we have been referred to our local CDC for various test including an ADOS.  we have seen a psycologist and she saw how my son behaved(he wouldnt come into the testing room to start with and when he did he hid behind me, pulled out the chair and hid behind that for most of the hour.  he wouldn't give any eye contact to the lady.) 

my dilemma-  the SaLT wants to view him in two different settings to see how he behaves.  the problem is  if someone comes to the house that he is unfamiliar with he will hide under his dinner table or go in his room.  if they come out to view him at his nursery i am concerned that certain staff will not report his behaviour in the same way as they have to me.  e.g one of the teachers can change her story depending on who she is speaking to and contradict herself.(thankfully i record the everything if i needed any proof).

i had suggested the play group he went to for speech therapy but thsi will not be runnning during the assement period.

should i bite the bullet and let them view him at nursery and if the teachers don't report accuratly go back to the profesionals diagnosing with the recorded information or should i avoid the nursery all together.

with regard to the nursery staff they are reporting the same behaviour that we see at home.  e.g there was a puppet show for xmas on at school and he had a meltdown because he didn't want to go.  he has also avoided today having a photo taken(he doesn't always like unless he is happy/on his terms.)

Catherine