Set all your items out on the counter so you can quickly size up what you have. Prep the individual ingredients: slice the cucumber, cantaloupe, kiwi, and pepper, etc. (For this board, I cut a "mouth" out of each cucumber slice with the lid of a marker, and cut large sheets of cantaloupe into small bat shapes with a mini Halloween cookie cutter.) Begin by placing the berries, mustard if using, and any other dips or wet ingredients in small bowls. Position those in the middle of a large serving board.
Grab one ingredient at a time and start to fill in small sections of the board. For visual appeal, try to place items with contrasting colors next to each other, and for instance, if you have two green items, try to place them more or less on opposite sides of the board. Keep adding items and working your way out to the edges until the board is full.
Add fun decorative touches, like candy eyeballs, mini chocolate chip "monster eyes" or "mouths," and possibly small plastic spiders, vampire teeth, etc. (As long as you're serving kids old enough to distinguish the food from the decoration, of course!)
Add a small knife or serving fork for each cheese, and small spoons for dips or berries as needed. Enjoy!