If you have the resources to get your members in the same room, you should absolutely do it.
It will jump start your community efforts. It will build strong bonds between members. It will dramatically increase activity in your community and present great content opportunities..
It's far easier to develop online communities around offline connections, than cultivate offline friendships for online connections. Facebook thrives on this.
It’s also a lot easier to ask someone to join a community face to face, than via the internet (it’s better to ask them via the phone). A real-time interaction gives the online interactions more validity. The internet element of the community isn’t treated in isolated governed by quasi internet-rules.
If you can get your audience in the same room, you will be doing far better than most communtiies.