My son's 3rd bday was construction themed. I'm a tightwad too. Your ideas sound very cute though. Here's what I did and where I spent my money:
- made my own cake. Covered it with chcolate cool whip, sprinkled ground up oreos in some spots, used wooden trees from a train set, put 2 construction toys and a construction guy (a new toy) on the cake. Put sand in the back of the dump truck - not sand, but ground up nutter butters. Got pretzels and made a stack of "wood" on the construction site. I could email it to you if you want (pm me if your email). Or google search "construction themed bday cakes" and you will find other ideas. (The look on his face was wonderful! He was so surprised by the cake. He thought it was really dirt. Hilarious).
- got $1 fabric tool-belts at Home Depot and used fabric paint to write kids' names on them days before the party so they'd be dry.
- each tool belt got a $1 measuring tape I got at the craft store and an inflatable hammer (amazon.com) I also got cheap plastic yellow construction hats from amazon.com. They only fit the kids' heads, but oh well. If you wanted, you could have the kids paint or marker on the hats, but you'd have to use Sharpies as they're a high gloss plastic.
- I did one game not really having anything to do with construction - but the kids had to pop orange and white balloons and find the balloon with the number "3" inside it (b'c that's how old my son was turning, and he and all guests were able to identify numbers and pop balloons, easy enough).
- decor: orange and white balloons, orange and white crepe paper I swirled here and there so it looked like construction zone cones. Some construction stuff you see is black and yellow. Some orange and white. Here in Tx all the construction cones I see are white and orange, so that's why I did those colors.
- oh and my plates - I got orange and white paper plates, napkins, and forks and knives, spoons. Plain white and plain orange worked fine. I also considered buying construction plates but they cost 3x as much.
pm me with any questions you have. I would love to help out any way I can.
It was back in April, but look in my old questions. I asked about construction themed party ideas. I know a lot of people gave party game ideas.
HATS I bought: $2 plus $2 ship&handling! http://www.amazon.com/Child-Construction-Hats-12-Pack/dp/...
CONSTRUCTION toy/guy I put on the cake: http://www.amazon.com/Mighty-World-Skid-Steer-Set/dp/B001...
HAMMERS i bought: http://www.amazon.com/Fun-Express-Inflatable-Hammers/dp/B...
A very cute cake you could probably make: http://www.just-baked-cakes.com/wp-content/uploads/2009/0...