For KS1 I wouldn't stress out too much about this. You've got some good ideas here. When I did this topic it was Year 6 and we looked at 'Flora and Fauna' (flowers, foliage, insects and other animals). weather in these areas. We built a huge collage showing lower, middle and higher levels and how the foliage/insects/animal life differed. Lots of maths work with rainfall and measuring temperatures, comapartive sizes. We made poems and did lots of art work obviously- leaf prints (which would be simple enough to do withyour age group) went down well I remember! Science we looked at different sub-groups-classifying. Can't remember the name of the book I used as a stimulus -I remember it was an American import with some beautiful pictures about the story of the trees.