How exciting for you!!! I suggest a good smaller bag to carry your essentials. I like one of those mostly flat, cross-body smaller bags for essentials like credit cards or lip balm (these would be my essentials). I do not do the large bag for water, snacks, etc. as I like to travel light.
Good walking shoes - probably a couple pair per person so you can change them up every other day. Wearing the same shoes every day can be hard on your feet and body.
General advice - look online for park maps to get the lay of the land ahead of time. You may still want a map at the parks but this will give you a head start.
Decide before you go which parks you are going to on each day and plan FP+ ressies and meal ressies well before your trip.
Plan something special for the two of you that commemorates your marriage! Whether that is a nice dinner at a signature restaurant off the beaten path or even just a relaxed stroll around the World Showcase in Epcot or around your resort, plan something that does not have a hectic pace so you can enjoy each other and your surroundings
Having been to WDW many times, I find that a person can get carried away by the rides and attractions and hectic pace and your trip can seem so fast and over so soon! Much like many who get married and have a traditional bigger wedding, you plan and plan for so long for a WDW trip and the time seems to fly by and details are forgotten due to the pace of things. Take a breath and enjoy it while you are there because it goes by much too quickly!!