Hi S.S.
I asked my mom - she's a dental hygienist. She said if there are no problems it's more of an evaluation. They will come in and get to sit in the chair and go up and down. my mom will sometimes put gloves on the kid and let them count her teeth and then she'll count their teeth - but she can also feel with her fingers for placque, buildup, or sores etc.
depending on the kid's tolerance level, she might show him the mirror or the scaler and then use it a little bit in the mouth. She'll have him open and close and bite a piece of paper to see jaw alignment. She'll also brush his teeth, just with a toothbrush.
If the kid gets upset - it stops. Any dentist that advocates holding your child down while he does dental work should NOT be practicing.... especially with kids!!!!!!
When the dentist comes in he'll look in the mouth with the light and check his glands, jaw alignment and maybe touch a bit with the scaler.
That should be it.
he'll get a toothbrush and a sticker.
The goal is to get into the habit of the dental visit and to get him comfortable with what goes on. it's also to check and make sure everything is ok with the enamel, bite and alignment because they can catch alot of things at this age.
Good Luck.