Let your assessor know and start your speech by explaing you have a stutter. I've always just started with a joke like saying "I have a stutter so if you don't catch what I'm saying on the first try. You might get it on the 3rd or 4th." It let's the audience know you stutter and it's not just because you are doing the speech. And that you are ok with it and they don't have to feel awkward about. It takes alot of the tension out of the room. This is maybe not great advice but If you are an adult have a couple of beers to take the edge off