What to teach preschoolers who just start to learn French? Well, what would you teach them if you were teaching them English? You can proceed along the same lines, except you do everything in French. This is important. The more the children use the language, the more comfortable and familiar they will become with it. The immersion method - using the language directly with picture cues rather than other language translation - will lay a strong foundation for further French language study.
To begin with, you can teach the preschoolers things that they are already familiar with in the English language and things they can easily relate to. Use some of these suggestions to get started.