my son has unused tuition + 2024 tuition fees. How do we maximize this for both of us?

Your son's 2024 tuition will automatically be used if needed. He can transfer the remainder to you (up to a maximum of $5000 federally). If not it will automatically carry forward.

Tuition from previous year's can't be transferred. It will be used automatically (if needed) or carried forward.

The tuition transfer from your child is non-refundable. This means you only can use it if you need it to reduce your taxes owing. If you don’t have taxes owning, you won’t get the credit. If you only have some taxes owing, then you'll only get enough tuition transfer credit to reduce your taxes to zero.