Congrats on your speech topic. It's always nice to see people spreading the good word on rats as pets.

Does Stewart or Oreo have any experience with other people? Or traveling? Or noise? How do they react? I ask such things because I personally don't think it'd be a good idea to bring your rats anywhere, unless it was needed - ie, the vet. Rats are very suseptable to the slightest illnesses that we, as humans, don't even think about. I don't think you want Stewart or Oreo getting sick because you brought them to a speech. Also, when a rat is brought into a new situation, nervousness can set in, leading to illness. Think about when Stewart or Oreo first came home - they weren't automatically wanting to jump out of the cage, run around, and crawl on you, were they? It takes them a while to get used to the new surroundings. If you don't have to have them in a new surrounding, I'd advise you not to then.

For a visual aid? How about making a stuffed rat? Seriously, though. You could have visual presentation - on a board, or powerpoint, or something similar - that shows pictures, interesting facts, etc.

I think your introduction sounds great. However, I'd leave out "but today I'm here to talk to you about pet rats" because it's almost stating the obvious. In the introduction of the speech, you want things to start to unfold, but also keep some things hidden for later in the speech! Just a tip, though. You don't have to listen to me. But personally, if I was listening to a speech with that very first line, and then 3 sentences later them telling me they're going to tell me why they're giving me this speech in such an obvious way, I'd go to sleep.