I think the best man would normally be on hand to organise things for the wedding as well. I think there are times when the couple and family would really like to be able to delegate some tasks, and it may be good if you are on hand to take up the slack. For example, you may be able to offer the service of a 'mail merge' for generating the wedding invitations, or getting them all posted, phoning around for quotes and details on wedding cars, etc.
I believe the buck's party is also usually up to you to organise. I thnink a buck's party really doesn't have to be sexual or drunken in character. I think it should be catered to suit the groom. No reason for it to be inappropriate or embarrassing to the people involved. Of course some people really like it tawdry. I would take the lead from the groom on that.
