The first thing I thought of was to place the two smaller cakes on cake plates of varying heights to give the arrangement some height.  It would require just two plates that you could find at any department store.  I am sure Martha would have some stunning choices at Macy’s!  The larger cake could just go on a disposable cake round or on a glass platter.

And I love the simple floral arrangement with candles.  You could, of course, substitute in a bride and groom topper.  Or you could use monograms as seen in this prior post.

And there is a wealth of great ideas for the garland seen above.  You could use wired ribbon, flowers, petals or fresh greenery.   Or make it seasonal with pine garland, paper hearts, lilacs, etc.