Meet with your Engineer
Arrange a meeting with your engineer.
Discuss the aims of the project(s) you want to undertake.
Introduce your engineer to the class or group of students, remembering that classroom management is the teacher's responsibility. The engineer may be happy to discuss what they do as an engineer and give a brief explanation of engineering.
Discuss your project ideas with the engineer. In this example from Otatara School students put their ideas into a matrix as a way of evaluating the merit of several suggestions.
Record the outcomes of the discussion with your engineer and make sure you have completed what is necessary before their next visit. It may be possible for the students to email questions to their engineer.