Most wedding bands do know what to do for the big day and they are fairly experienced and equipped to handle most of your requirements. You also do need to delegate some of the responsibilities concerning the arrangements for your big day. However, the fact is that they will have no idea about the musical preferences of your group and consequently might not be able to come up with a program that is widely appreciated.
If you are really pressed for time and would prefer to have the band take on most of the responsibility of organizing the music, then you should at least have a written script for the entire program. Ask the band to prepare it for you after which you can approve it or make necessary changes. The advantage of doing so is that you can get a friend or family member to oversee the activities of the band on your wedding day. You can also link payment to the band to its ability to stick to the program.
You will save a great deal of time and effort if you just took the time out to brief the band about the musical preferences of you and your soon-to-be spouse. You could then ask the band to choose songs based upon these preferences. You do need to acknowledge the fact that wedding bands have a fairly good idea about what works and what does not. If they urge you that certain songs always get the guests dancing during the reception then you ought to pay heed to them!
You should also make it a point to listen to the final music program at least once or twice. Get trusted family members or friends along with you so that they can provide you with second opinions. Once you have finalized the program you can sign a contract with the band and pay the necessary deposits. You can then focus on other aspects of your wedding that need your immediate attention, knowing that you have the musical aspects all charted out.