My kids love learning games. Maybe you could make up games similar to Eye Spy. I call it Blues Clues because it makes you think. We act out what we are looking for, use words, numbers, letters. Look for whatever you can think of… vehicles, colors, letters, items that make specific sounds or begin with a specific letter. I give my kids hints and then they try it on their own. When they get answers, you could reward with little things from the dollar store, popsicles, hard candy, bouncy balls, cars, etc.
Kids love arts and crafts. There are new paints that dissolve and are washable for the sidewalk. You could get a bunch of cheap construction paper from the dollar store and let the kids go to town painting. They could even paint their own clothes. You could get a bunch of really cheap kids shirts from a craft store, dollar store or Wal-Mart and all the kids could use the paint. They could make whatever design or maybe make pirate themed items for the treasure hunt. You could give them examples of simple things they could make like a ship, treasure chest, sword, pirate patch, parrot, etc.
If it’s warm enough outside, you can probably just get out the hose and some old towels to clean off the kids hands. You can keep all the activities outside to keep the mess out of the house…lol.
I recently spend out $5.00 on a gallon of Magic Bubbles and a bunch of bubble toys. About 10 kids from the neighborhood all gathered in front of my sidewalk and all played in the bubbles. They tried to catch them, pop them, count them, chased them all over the yard. I recorded them playing on video and took tons of pictures. It was really cute to see them play, share and trade bubble wands.
Kids love science and exploration. I found a bunch of really cheap magnifying glasses at the dollar store. They were only a dollar each. My boys love going outside to look at rocks, ants, worms, leaves, dirt, our frog, etc. They lift up the landscaping bricks and there are tons of little creepy crawly things beneath them. They’ve examined our puppy, looked at the lines in their hands, acted like doctors. I used those times to tell them about their bodies, plants, animals.