The presentation is the most important part of your lesson. Do not rush through this part of the lesson; this is where you ensure your students gain the confidence to speak and use the language. Without sufficient time spent drilling, students will be unable to do the practice exercises.
In the presentation section of your lesson you need to show the meaning of the language, test the meaning of the language, drill the language, and make sure it is written up on the board, unless you are teaching very young children. However, given that three year old children can recognize simple words and letters, I would make sure the words cat and dog are written underneath the pictures too. Sometimes it's very easy to underestimate young children.