For the watermelon cocktail: You can substitute Thai basil or any of these lemony herbs for a more complex flavor profile: lemon balm, lemon verbena, lemon-thyme, or lemon-basil.
For the fluke dish: You can make everything 1-2 days prior to your party—just simply slice the fish the day of.
For the grilled peaches: This can be done in its entirety before guests arrive. Grill the peaches, cool to room temperature, and continue with the recipe; wrap it in plastic and leave at room temperature until guests arrive. Other fruits that can be grilled as substitute are watermelon, cantaloupe, nectarines, and halved citrus.
For the grilled pork belly: You can braise the pork 4-5 days in advance then cut it into slices the day of your event. You can cut the corn the day before the event. The cherry-jalapeño relish can be made in its entirety the day before as well. The day of the event would consist of sautéeing corn, heating the pork on the grill, and topping with the relish.
The entire dessert: Can be prepared 1 day in advance