You might try to get PS at Rose & Crown. They can seat you outside along the edge of the water. If you make PS for around 8:30pm, you should have a perfect view of Illuminations. When you make the PS, tell them that it is for a wedding party and that you really want to sit outside. Normally, it is just a luck of the draw thing, but since you have a special occassion, they may try to accomodate you.