I am actually not alright with Wan Shi Tong knowing Rei's identity as Sailor Mars. It's a canon fact that the characters civilian and Senshi identities are protected by some divine power strong enough to stop their own family from recognizing them. As such, I'd really rather not have him know that right off the bat. It's sort of a big reveal for the character and I'd rather him treat Civilian/Senshi identities as separate people.

As for Rei: She's a quiet, reserved shrine maiden. And Mars is the reincarnation of the Goddess of Flame, Passion, and War, as well as the princess of Mars.

Krillin, feel free to know whatever you feel like Wan would know.