You can get free buttons with groom Mickey and bride Minnie at any ticket window or service desk in the parks. There are other wedding pins that they sell at the pin stations. I got a Mickey and Minnie DFTW pin at a gift shop at GF last year.
I wore the free pin (DH didn't want to and that was o.k. with me) but we didn't get any special treatment. A couple "congratulations" and a very funny thing at our day-after wedding brunch but nothing "special." Some couples get special attention, put on rides first, upgraded room or dining seating, but others get nothing. So, my advice is don't count on it and you won't be disappointed.
Still you will have a magical honeymoon - it's Disney after all