Should I bring my boyfriend to a wedding?

A very good family friend is getting married next month, and I asked my mom if it was okay if I brought my boyfriend as a date. She said we would have to wait until the invitation was addressed. Well it came today and did not say Miranda and date on it. So my mom said it would not be right to bring him. The wedding is huge and like 800 people are invited, and my sister is even in the wedding. I have been dating this guy for a month and the bride and groom both know him. Is my mom right, or is it okay to bring him?