have they agreed to assess or has he been put forward for consideration?
We've just found out this week the LEA are going to carry out a statutory assessment, I've got a huge form asking for parental advice and any reports etc they haven't recieved, and to name anyone i would like them to contact.
Its not compulsary by any means, but You know your son best, you know how bad he is on his worst days and you know what his strengths and weaknesses are, you know what areas he needs specific support in, so yes you should have some input!
I'm halfway through, but mainly I'm managing to condense it and atually use the form and write it by hand! theres a couple of sections I'll have to type, namely the ones involving school, relationships with staff and children and how he compares with children the same age...
I've been advised by his preschool advisory teacher to think of elijah at his worst and write it from that perspective, becuase thats teh level of support he actually needs, to ensure the bad days decrease and he can reach his potential.
My son is 4 in july, barely verbal ASD he's also poor concentration wise, he flits AND he gets stuck on things, and don't et me started on the stims... 
any pointers I can offer I will though! just ask!