Assign each table a different anniversary year (i. table 1 would be anniversary year etc.) and let the guests at that table write notes to be opened on that particular anniversary year (a unique alternative to a wedding guest book).
If you were to use drift wood this would be awesome for a beach reception style thing. Very natural, but striking. Drill holes in wood, place tea lights. Beautiful outdoor table center piece for the picnic table---AROUND THE GARDEN POOL