Teaching about whales and dolphins should focus on whales and dolphins being mammals, not fish, that breathe air through blowholes, have no fur, and give birth to live young. Key concepts include learning about different types like toothed whales (e.g., orcas) and baleen whales (e.g., blue whales), their diverse diets (seals, fish, krill), how they communicate with songs, their importance as the largest animals on Earth, and their endangered status requiring conservation.