I nanny for a (now) 9 year old girl. For her ninth birthday party her mom and I had a heck of a time coming up with party ideas. Finally we thought we could do a scavenger hunt of sorts. We weren't  sure how to approach it but then decided on a Secret Agent theme. We would have the girls solve  clues to find tools, and more riddle to go to certain locations during the party. Everything just snowballed from there. We told the girl that we had a surprise for her party but that was it. We knew  there were going to be 6 girls total(all we could fit in the car) so we planned accordingly: Step 1: BUYING SUPPLIES-we went to hobby lobby and bought 6 different colored t-shirts($2), 6  cloth bags($.50), cloth tranfer paper, fabric markers (less messy than paint!), and 6 name tag holders. Then we went to Walmart and Party America and bought various "spy" type things(6 of each, of course): tiny magnifying glasses, dark sunglasses, small notepads, pens, small mirrors, nose and glasses disguises, etc etc. Step 2: SET UP- We thought of secret agent names (we went with a bird theme: secret agent eagle, hawk, canary, finch, etc) and printed them from her computer onto the transfer paper (make sure you mirror-image the letters!!!!) We also printed out a little logo "(b-day girl's name) Spy Academy" and tranfered those to the t-shirts (they turned out SO cute!) We also printed out a larger copy of the logo for the birthday cake and took it to King Soopers to have them transfer it.  I then cut out  cardstock squares corresponding to the girls' colors (each had an assigned color). On these squares I wrote out the clues. On some I did simple rhymes, others had missing words, and others incorporated the tools they will have found (like mirror writing). The color of the Clue dictated which girl got to read it and try to figure it out (eliminating anyone being left out). We also called ahead and arranged for the cake to be picked up(by the girls), also reserving a spot for six girls to try out a rock climbing wall ($2) and do laser tag ($5). We also put them in a hotel room for the  night.  Step 3: THE PARTY-When the girls arrived we gathered them in the living room to explain their  secret mission. Her mom and I had also made shirts for ourselves, we said we were just supervising  for the "big boss spy." We told them only that they were spies and gave them colored cards with  their new names on it. We explained to them how the colors of the clues worked. Then we gave the first clue to the b-day girl. It led them to the dryer where their shirts were, plus another clue. They all put on their shirts. The next clue led them to their fabric bags. The clue after that told them they  had to decorate their bags. While they did that (took about 30 mins) we took eaqch one outside and  took a picture of them in their outfits and a disguise we had put together beforehand (a trenchcoat, fake nose, and a hat). While they finished their bags I printed the photos and made quick ID tags for them to put into thier tag holders that they would find later. After the bags were finished they  finished their hunt to find all their tools around the house and outside. By the time they had found everything their bags were dry and their photos were finished. As they put everything in their bags we put their photos in their tags and we were ready to go.   The next clues led them first to King Soopers where they were given a secret song to sing to the  baker to get their cake. After that they were each instructed to find one food and one drink to have for the night. (ranged from box of cookies and soda to loaf of sourdough bread and water--no  kidding!) Then they were sent to the local Brunswick Zone to play a $5 round of laser tag. Then off  to McDonalds where they ate dinner and found another clue in the play place. After dinner they were off to the mall where they have the $2 climbing wall. None of the girls had done that before so  that was a blast. At least one had to reach the top to get the next clue.  During all of this we had also given each girl a list of items to find for a scavenger hunt (penny, hair clip, rubber band, etc.)  to keep them entertained during the car rides/waiting in lines.  We finally ended up at the hotel (about 3 hours later) were the girls went to the room to open presents and eat cakes. After that they got to go swimming while the adults had a nice little break (watching them, of course). After swimming we gave prizes for who ever had the most items from the scavenger list. (dollar store prizes, of course). Then the girls entertained themselves(and ate their snacks) for an hour or two more until we made them turn out the lights.  This party was an absolute hit for all involved and if you really wanna WOW your kid, this is an excellent way to go. Overall it was no more than $200 for all supplies, dinner, activities, and the  hotel. BTW- most of the clues were planted simply by one of us running in (inconspicuously) before  the kids. It really was a lot of fun for all involved, and I know the kids were all talking about it long after the fact. Now our only challenge is topping it next year, though I think we will probably do the  same sort of thing again, maybe with a candy factory tour or a museum thrown in, LOL. Good luck!