A conference sounds like a good idea and a change in teachers may be the best decision.
In case you are concerned that you might get emotional during the meeting, it may help to prepare and organize before you attend. Start with a written outline of concerns - headline specific issues that might come up and have some point-form notes under each issue that you want to make before the meeting ends. You could note anything relevant from his last doctor's check-up (including the doctor's opinion that he's right on schedule, developmentally, for a 3 4 y.o., if something like that was stated). If there are reports or assessments from last year's Pre-K teacher, bring them with you, especially if they remark on his classroom behaviour. Examples of any "work" he's done at home that might differ a little from what they see at school, in terms of artwork or writing that might show motor control, attention to detail, etc., in case there is some issue about his academic readiness.
Having that kind of "portfolio" in front of you may help you stay on track if you start to feel overwhelmed during the meeting. Best wishes with it.
Ed. to correct typo - he's 4, not 3.
Edited by ollyoxenfree - 9/6/12 at 6:15am