This should not be a concern. You will find that gardens visitors immediately perceive that a wedding is in progress and are quite respectful. Staff is also on hand to guarantee your reservation. Certainly, as long as the decorations are removed after the ceremony. There are trash cans near the entryway.
Many couples choose to take their photographs before the ceremony.
This seems to work well, but it is your choice. There are many, many photo opportunities in the gardens. There are standard electrical outlets at the site. All are GFI protected for your safety. Staff will indicate their locations.