If public speaking is part of your anxiety, there is a group called Toastmasters that allows you to learn and practice public speaking in a supportive environment. Part of what you practice is impromptu speeches, which might be good practice for those "mind goes blank" moments you describe with the parents. Unfortunately, this won't help you for Monday specifically but for future years perhaps.

I hope things go well for you. Perhaps it would be helpful to remember that you're not speaking to a hostile crowd. You're their children's teacher and they want to and will like you. No need to be nervous when you're speaking with friends.