These should be in your normal narrator voice. However, if you're using special voices, most of the tag lines can just be left out. Remember to switch back to audience focus for tag lines you retain. If the characters are supposed to be at different heights, you can also look upward and downward. Then close the book, again show the cover, and repeat the title.
Good reading requires practice.
A tape recorder and a full-length mirror can give you valuable feedback. Also helpful is listening to professional storytellers and readers, live or on tape. But don't take it all too seriously. Even without trying, you'll get better as you go. Relax, play, enjoy yourself.