In that case, you will need to build the array of attendees separately from the trigger module.
To do this you need another set of Iterator-Aggregator modules (advanced), or simply put other non-attendee data in another spreadsheet and use another Google Sheets module to fetch the information.
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!