you have to be mentally ok if all hell breaks loose, the mouse breaks, you forget what you're talking about and someone starts laughing out laud at you. Cause really, even in this worst case scenario, if you just laugh it off, no one is going to care what went wrong. Everyone wants the awkward situation to be over just ad badly as you do because they can feel it too.
You don't want to memorize any speech material, you want to know it well enough that you can just talk about it without reading from the paper. This is the sure fire way to get out of any bad situation. If you think you need to recite every word as you wrote it down, then you're setting yourself up to fail and you have no fall back.
And the only way to practice public speaking, is public speaking. Try it first in front of family members.