The Morning After

The bit nobody plans, and the bit that decides whether the whole thing ends well or ends with your father-in-law carrying trestles in the rain.
Somebody Has to Clear the Field
Marquee companies de-rig on Monday. Hire companies collect on Monday. What happens on Sunday morning is entirely down to whatever you arranged, and if you arranged nothing it falls to whichever relatives are still standing.
Pay somebody. A two-person clear-up crew for four hours costs less than most of the flowers and it is the single best money spent on the whole wedding.
Do the Breakfast
A relaxed second morning is the part people remember most fondly, and it costs almost nothing. Bacon, coffee, whatever is left of the cake, in whatever room is available, with no schedule at all.
It also gives you time with the people who travelled furthest, which the wedding itself never does.
What Goes Missing
Cake knives, cake stands, the guest book, somebody's jacket, and every single vase. Give one person a box and the job of walking the site before anyone leaves.
And take the flowers home or send them somewhere. Leaving four hundred pounds of arrangements in a field to be composted is the most common small regret on this list.