Students design an inter-active pathway using touch switch technology. Students set up a table in the hall, where they explain the science and demonstrate how they designed, built and programmed their exhibit.
Most of the activities should be do-able within the context of normal classroom activities. This should not involve extra duties/administration for teachers. Costs for Christmas lights and control systems are minimal (using Christmas lights provides cheap, off-the-shelf lights/electronics which come pre-approved for safe outdoor use).
The visual aesthetic is determined mostly by how the representational plants and animals are arranged and by the associated lighting effects - the quality of workmanship for plants and animals need only be very agricultural/crude.
The use of SOUND is extremely important in creating an emotional audience experience.
Lots of other possibilities depending on the creativity/interest of teachers/students/community. The ideas to be student-directed as much as possible, with big people focusing on the practicalities.
It would be great to find funding/sponsorship for lights/materials.