My son was turning 4 yrs old and loves back hoes, bull dozers and dump trucks as well as fixing things. So a construction party was the way to go for us.  I found dump truck invitations at a local party store where I picked up plates and napkins to match as well.  I rented the town hall in our local town for no cost at all. I got black and yellow table clothes to decorate each table and dump truck balloons as center pieces. I was able to get caution cones from a local township that I used to block off one section of the hall with.  I also used caution tape that I was able to buy at a hardware store in which I attached to the cones to make a barrier around the work site I put together for the kids.  With in the work site I had card board brick blocks that the kids got for christmas one year at the first site.  This site was labeled brick laying ahead hard hats required". Which i displayed on poster board and hung on the wall above the bricks. The idea for the 1st site was to build a house.  The 2nd site I had a big card board box I got from the washing machine I had to replace at the house. I painted the box all white ahead of time and drew a door on it to make it appear as if it was a house. i then bought a pk of foam rollers from oriental tradig for $5.00.  All the rollers had different patterns on them.  I bought washable paint and little paint trays for each roller. Paint shirts were waiting at the site along with the paint.  This site was "caution wet paint ahead...paint shirts required" and hung from poster board above the site as well.  The idea for this site was once they built a house they needed to paint it. The 3rd site was big plastic bolts made of three different sizes with nuts to fit each size bolt. I bought a big bag of these from oriental trading for $5.00 last year to have for the kids around the house. I had my boyfriend cut strips of masinight board (he had left over from a job as he is a contractor) and then drill holes in each end of the board so the bolts would fit down in and you can attach more than one board at a time and still allow the kids to screw on the nuts. This site was labeled "construction site straight ahead". the idea for this site was to have the kids create different shaped windows for the house they just painted.  They were able to make triangles squares and diamonds out of the wood and bolts. The last site was building a car (kinda like the home depot projects you can do the 1st saturday of each month) I was able to find the cars on kwik craft.com where I purchased each one for $1.99 each.  I had this craft on a table with hammers and washable paint.  This site was labeled "hard hat zone...adult supervision required."  The kids loved this site the best. The idea for this site was once you have a house you need a car to park in the driveway. I had sub trays and chips for food as construction workers usually pack a lunch. I had a cooler filled with ice for the soda juice and water and left open for everyone to get to.  As the kids arrived to the party I handed out hard hats I got from Oriental Trading (12 for $5.00) and home depot aprons I was able to purchase for 77 cents.  Once all the kids had arrived I sat them in a circle and handed out time sheets (paper I found in yellow and black with their names and 4 boxes written on it) and explained to them that they had 4 jobs to complete in the construction zone and each time they completed a site....they needed to stamp their time sheets. Once all 4 boxes were stamped they were to return their sheets to me to get paid for all their work. Payment for the kids was goodie bags filled with a small caution cone i found at the dollar store that said "good work" gummie tools a ruler pencil a chubby paint brush with washable paint and a sticker sheet with all kinds of construction trucks.  I had the goodie bag wrapped with ribbon and fake money attached to the outside of the bag labeled with each kids name saying "GREAT JOB". I bought a construction site cake that was really made out of cupcakes for all the kids and adults. I had the kids then do a pinata that I was able to find on birthday express of a bull dozer for $14.99.  Over all the party was a big hit and each parent called the next day telling me how their kids were wanting to help work around the house and fix all kinds of stuff.    "