Hello astro.
I'm an SLT.
What will typically happen int he assessemnt is:
detailed case history (talking through early development/ your concenrs etc)
a look at his attention and listening skills i.e. how he attends to self chosen/ adult led tasks and how he responds to support to attend.
a look at his:
play & interaction skills
understanding of language and non verbal skills
expressive skills- how he makes his needs/ thoughts etc known e.g. with words and or gestures etc.
speech sounds (pronounciation)
the SLT should ask for yuor input throughtout the assessemn i.e. ' is this what he would do at home?/ what else would he do/etc.
The SLT should be able to tell you why they are doing what they are doing as the assessement unfolds.
Most of the assessemtn may be informal i.e. through play/ use of toys etc to illicit responses from your DC.
The therapist may try a number of approaches in order to engage and help your DC.
Do ask if you are unclear as to what is happening- also do let them know if he is not showing skills you have seen in other contexts.
at the end of the session ensure that you feel confident as to the outcomes of the session i.e. where DC's areas of strength lie/ needs might be and how the SLT might recommend supporting these (if appropriate).
Ask about waiting times.
Ask what you can be doing to support DC's skills at home, and ask the SLT how they might link with nursery to support staff in helping DC too.
rushed response but hth