I was going to suggest geocaching, but you'd have to take them to a local park or something. And then I ran across this, which sounds pretty doable: http://www.geekwire.com/2013/reinventing-scavenger-hunt-app-brings-hightech-twist-fun-family-game/

I've done quite a few treasure hunts. One way is to find a word that tells the final destination (where the treasure is hidden) and hide letters around that have number on them that correspond with a number on a set of lines. 1.__ 2.__ 3.__ etc. When they find all the letters and fill out all the lines, then they have to unscramble the final word. Only will work if the final word is not easy to guess after finding just a few letters. Another way is for the first clue to lead you to the second, etc. until the final one.

Thanks for the replies! This needs to be inside and around the house as I don't have a car big enough to cart 7 teenagers around.

You could even have a "treasure" at the spot of each clue, and the letter would be the first letter in the name of the treasure. You could hide the next clue to the next location under the treasure. That might take some doing. Believe it or not, I do this kind of thing for a living.

I just made one at this site:

http://www.treasure-hunt-ideas.co.uk/create-a-treasure-hunt/start

I am going to put a bag with an envelope for each boy containing a scratch-off lottery ticket and a candy bar in the 11th and final spot.

I love treasure hunts!

Thanks for sharing the site. I think I will use it for my DDs 13th this summer. If you've ever done any type of treasure hunt you probably already know this, but they go thru the clues waaaaaay faster than you can imagine, so do more clues rather than less (or maybe my clues are just lame so they get them quickly?).