Boy getting married without his parents approval

I am a new Muslim. I am currently married to a Christian and seeking a divorce. After divorce and iddah time is final, I desire to marry a Muslim man. It is the same person that helped lead me to Islam and helped me with my Shahaadah.

The problem is that I am a Caucasian American and he is an Arab Egyptian. His parents do not accept me because I am from a different culture. I have been married before and I am not Muslim by birth. His parents want him to marry a virgin from his culture. Me and him tried not to, but we have fallen in love and want to marry. He is 25 and I am 26. In order to keep his parents desires for him, I am willing to accept a polygamous marriage. But they still don't approve. He is now asking me to marry him without his parents knowing, and tell them after the marriage. I want to marry him and he wants to marry me, but I do not want to start off a marriage with haraam ways. I want my marriage to be halal. Can you give me sound advice to this situation?