To get the most out of a Yes Day (which is usually celebrated annually), tell your kids about the concept, your ground rules and your budget a few days in advance to build anticipation.
Simple is fine. A Yes Day doesn't have to involve lots of planning or elaborate activities. Extra books at bedtime, a messy activity such as finger painting or letting the kids decide how long to stay at the playground are fun and free and can fill your kids with delight.
Many parents make the day device-free, which means Mom and Dad can't check their phones, either.
Children may need some prep for the first Yes Day, but not after that. Once they get the idea, they're likely to have plenty of requests for the future. To keep it fun, try waking kids up on a Saturday with the news, "Today is a Yes Day!"