I emailed DYS and got this response:

In regards to your question about the Nominator for the Young Scholars Application, in the past, we have had families submit forms from various sources; teachers, gifted coordinators, school administrators, and even family friends. You may want to think about using someone who knows your child and their abilities. Ultimately, it is to the family’s discretion to who they use as a nominator.

The types of questions that are asked in the nominator form include how the nominator knows the applicant, what they know of the applicants advanced abilities and how the applicant would benefit from the Young Scholars Program. You are more than welcome to share this information with the nominator so they can make the appropriate preparations.