If you have girls, I bet they would be interested in baking. You can decorate cupcakes and cookies. Maybe even learning how to sew or knit.
Boys wouldn't be interested in baking?
OP - if there are littler kids in the neighbourhood that your kids know and you know the parents you guys might enjoy organizing something for them too. Not as a job just as a let's all have fun outside kind of thing, though it depends on your neighbourhood/block.
Could do a neighbourhood scavenger hunt - if there are a bunch of younger kids yours could plan it, hide stuff, run the thing, etc. That can take a couple days - planning clues so all different ages can look for stuff, where to hide things, what unhidden things to find (you can have people look for a piece of paper you hide with a number on it and hide a bunch or have everyone have to tell what colour some porch chair is or find a specific kind of leaf or etc., etc.), then how long they'll have, rules, what prizes there'll be... silly little prizes for lots of things, first to find everything, last to find everything, shortest competitor, you can get dollar store stuff everyone likes, like a thing of bubbles (like to blow bubbles), glow stick, and everyone gets popsicles at the end.
You could do a neighbourhood newsletter, and task your younger ones as reporters/photographers, to go around and find out the neighbourhood "news" and ask littler kids if they want to draw a picture or write a poem or something and they could publish the stuff - the older ones would write, lay out, scan, etc., make it look goofy fancy. Stick it under everyone's door.
Or if you have any elderly neighbours, you could all adopt one for a day if you call and ask if you could visit - make cookies or banana bread or whatever, a pitcher of iced tea, go over and ask if you can help out with some chores in the yard or around the house they might not have done because it's hot - ask them about what they used to do when it was this hot out when they were your kids' age, ask them to teach you all a card game from their childhood, etc.