Let's pretend I didn't learn this info by forgetting about my prepped beans or deciding not to make them. Let's pretend I'm just Uber-Chef and know what I'm doing, OK? Your cleaned, sliced/prepped beans will last lots longer in the fridge than you need them to for this party.
In addition to prepping beans today (b4 cooking), I think you could make the whole salad on Friday, depending on what else is in it. I don't think beans would get soggy or anything, unless they're swimming in liquid. At least you could steam the beans today or tomorrow, and plunge them into ice water to stop the cooking, and prepare the other veggies today thru Friday, and assemble the salad with the dressing on Sat. morning.
Care to post the recipe?
If you're afraid of butter, use cream. ~~ Julia Child
As you cook, you enjoy omniscience about food that no amount of label reading can match. Having retaken control of the meal from the food scientists, you know exactly what is in it. (Unless you start w/cream of mushroom soup, in which case all bets are off.) To reclaim control over one's food, to take it back from industry & science, is no small thing; indeed, in our time, cooking from scratch qualifies as subversive. ~~ Michael Pollan