Thank you for the question!
It is not inappropriate since the Qur'an commands us: "O you who believe, be helpers of Allah (ansar Allah)" (61:14) and then mentions Jesus (A) asking his disciplies who would be be his helpers towards Allah. So it is a Qur'anic phrase.
The Imams (A) are called this because they wholeheartedly and fully served the cause of Allah.
However, if saying they are "ansar Allah", makes you feel uncomfortable, you do not need to say it.