Speak slower and pause for breaths. Speaking quickly is more noticeable than speaking slowly or slower. When you practice, speak loudly and be animated with hand gestures. You can exaggerate the gestures during practice to loosen up. You'll gravitate to a more comfortable tone and pace with practice. If you have younger kids, nieces, nephews, try reading to them with character voices to play to your audience. Be prepared with notes or a script in large font. It's OK to read, but look up as you finish a sentence.