Valentine's Date, too old?

Alright ladies. I've ran into a problem, I really need some help. I've been talking to this guy whose 5 years older than me since last school year. I'm a senior and I understand the big age difference might be a bad idea, but we went on a date this morning. I tell my mom everything but I didn't tell her about this date. Should I tell her? And if so how should I?