I'm a little bit confused about the protocol of 'engagement parties'. My boyfriend's sister is holding an engagement party, at a hall, free drinks, with a mix of guys & gals (it's not a stag and doe..) and I'm unsure what this party means in terms of gift giving? What would you do in this situation?

I asked my boyfriend (he is clueless when it comes to gifts..i know this firsthand).. but he says we just show up and celebrate. What would you do? Thanks!