How do you effectively co-plan lessons with a co-teacher to ensure equal participation?

My new school is looking for ways that related arts (music, art, and PE) can integrate math into their lessons easily. Any ideas or research that you’ve found that helps this work? We are doing this Kinder through 5th grade.

I will be having a student teacher join my classroom in August. What do you wish you knew from your mentor teacher when you student taught?