I will discount the lesson fee for permission to post photos of the lessons on social media.
If you will let me post photos of the lesson on social media, I can give a discount
I will discount the lesson fee for permission to post photos/ videos of the lessons on social media.
If you will let me post photos/ videos of the lesson on social media, I can give a discount.
SNSはほぼ和製英語に近く、英語圏ではsocial mediaと一般的言います。
投稿する内容も写真なのか動画なのかを指定したうえで聞くと間違いなく伝わると思います。