Selling alcohol from a mobile bar is governed by the same set of laws as a fixed premises business, such as a pub, so always make sure that you check with your supplier that they have the right licenses and permits.
Always remember that if you are not having a bar and are providing alcohol to your guests, you are not able to charge for it. You will also need to factor in that someone will need to keep an eye on it!
If you are providing your own wine then a wine merchant will be able to help you with the choices. Show them the menu that you have chosen and they can recommend wines that work perfectly with all of the dishes. A good wine merchant will also invite you to taste the wines too!
Most venues who have their own alcohol license will not allow guests to bring in their own wine, and if they do you will almost certainly charge 'corkage'. This is a charge per bottle of wine opened and can often result in you paying more than it would have cost from the venue.