Working with children to understand their reactions to new ideas and products is fun and challenging. Provided the task is engaging and interesting, they are highly responsive and give you amazing feedback.
However, there are a number of ethical and legal issues which you need to understand. Some of those issues vary from country to country, particularly differences in privacy laws and protection for children. If you are wondering about some of these issues, a document which is worth reading is the ASTM E229-13 Standard Guide for Sensory Evaluation of Products by Children and Minors (https://www.astm.org/Standards/E2299.htm) put out by Committee E18 on Sensory Evaluation.
In addition to looking at testing issues (with a strong focus on what you should consider in terms of a child’s cognitive development) this document looks at legal and safety issues you should think about. It is worth having a check list of these issues before you begin your research, to ensure you and your organisation have protected the children you are working with.
Beyond the research itself, you need to consider whether you want to use any quotes or clips showing the reactions of children to products or ideas. Many of us record interviews or group discussions for our own use, which is fine. However, if any of that material is to be used with a wider audience, either within your organisation or outside, it needs to used carefully and with parental permission. One approach some companies use is to take any quotes or clips and have a child actor portray the original child participant.