There is no harm in
waving during offering the Salam in this case.
It was narrated that the Prophet (peace be upon him) greeted a group of women and waved with his hand.
He (peace be upon him) meant, and Allah knows best, to make them understand that he was greeting them. However, it is not permissible to substitute Salam by waving. (Part No. 24; Page No. 124) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.