How can I tell my friends about the older man I'm dating?

I’ve gone on dates with older guys before and one of the first times I told a few of my close friends. When they asked me his age and I answered truthfully I got a less than positive response. Now I’m going on a date with this guy, I’m 18 and he’s 30, and of course I want to tell my friends, but I’m not sure how to go about it.