Outdoor weddings have become quite popular in New England. But outside weddings have their own special challenges. You always need a back up plan in case of rain. And you have to consider how your guests will hear the ceremony,especially if the wedding is large, as the ambient noises outdoors can be difficult to overcome.
The best solution is a wireless lapel mike, usually worn by the officiant but strong enough to pick up the bride and groom and virtually invisible in your pictures. A hand held wireless mike can work, but it will tie up one of the officiant's hands and can be a bit awkward. A mike on a stand takes care of that issue, but the microphone and stand will be prominent in all of your pictures.
Check with your DJ if you are using one. The best will offer a digital lapel mike.