Is it ok if my father is the (Imam) and I pray behind him and we are the only two praying?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

A woman while performing prayers has to stand behind a man not beside him.

Anas narrated that “One night an orphan and I offered the Prayers behind the Prophet in my house and my mother (Umm Sulaym) was standing behind us (by herself forming a row).” [Al-Bukhari]

Umm Sulaym stood behind Anas though he was her son.

This Hadeeth denotes that a woman has to stand behind men even if they are her Mahaarim (non-marriageable men).

Allah knows best.