Split Reception Problem

Here`s my biggest problem: My FH and I are very into heavy metal, and want to hire a band to play at the reception. However, our families are kind of old-fashioned, and won`t appreciate it. Therefore, we`ve decided to split the reception. The first 2-3 hours will be traditional music, appetizers, punch, cake, etc. After that, the band will come on and we (FH, I, friends, younger family) will relax with beer and pizza.

As I see it, I have the following options:

A) I can include the concert and everything on the invite. (I`m afraid that if I do this, grandparents will object. The band`s name is a little explicit. I want to avoid arguments.)

B) I can include only the first part on the invites, then insert a card inviting appropriate guests to a concert afterward.

C) I can pass word-of-mouth info about the concert.

If I avoid telling granny about the band, and she finds out, will she be offended? My mom offered to run interference and explain that it`s "kids` music," and they won`t like it. I don`t want anyone to feel lied to, but I also don`t want to hear about "the devil`s music." How do we strike a happy medium?

Anda