My kids love these kind of gifts, and they really can be as little or as much as needed, based on what the individual wants to spend.
National or regional businesses like movie theaters, museums, Chuck E. Cheese or other arcade based places, bowling alleys, trampoline or inflatable places all tend to offer gift certificates of some sort.
And as others have mentioned, places specific to their area may offer them as well. Not only tourist destinations, but smaller "mom & pop" places, too. Art studios may offer parent/child classes or kid classes. Local theaters, museums, recreation or community centers often offer a wide array of classes and day camps. You might call to see if they have certificates that can be used towards any event, or even if they have some specific to one type of activity.
My kids even enjoy certificates to their favorite restaurant or ice cream/froyo/donut place.
And even though this is a thing, not an experience, it is consumable at least---they also like the boxes of snacks you can get mailed to them that feature a certain country each month. Some are subscription based, but I know at least one of them lets you send just one box if you want. Universal Yums and SnackCrate are 2 that I know of, but I am sure that googling something like "snack subscriptions from around the world" will find more for you.
