Stage fright when speaking to the participants as the trainer

I would suggest saying not just what you think, but also what you feel, as both dimensions are needed for human understanding. Honesty and transparency, even when you feel unsure of yourself, can only contribute to building trust between the team and the participants. If by some chance, a participant from the group ridicules your expression of insecurity and thereby tries to undermine the credibility of the training team, simply allow the group of participants to be the judge.