I always offer the nurseries I work with a poster a week or so before the photography sessions. This way parents and children know I am on my way and can think about their outfits (some children have been superheroes, some in their favourite party clothes/best dresses and others in nursery uniform)
The children can choose to bring props with them if they would like too. Some children are photographed with their favourite cuddly toy-I take a few pics with their chosen toy and this makes them at ease with the camera to then try other poses and ideas. The children love my new massive camera props as then the tables are turned and they are the photographer!