Use yellow construction site tape instead of streamers, and decorate with yellow balloons you write messages on like "caution" and "danger overhead."
At lunch time, ring a bell or blow a horn. Give each child a bagged lunch. Have lunches packed with different kinds of sandwiches and let them trade lunch items so they get what they want. Include a piece of fruit or veggie sticks, juice box and another yummy treat.
Prepare Rice Krispies* Original recipe. Separate the mixture into different bowls. Using food colouring, colour the mixture different primary colours (like plastic building pieces). Press the mixtures firmly into cookie sheets and let set. Cut into different sized blocks. Let the children build their own creations using Royal Icing as the mortar. Depending on the number of kids, you'll need at least one large quantity recipe.
In a medium bowl, beat together 1/4 cup of meringue powder and 1/2 cup of water until soft peaks form. Gently stir in 4 cups of confectioners sugar until fully incorporated. Consistency may be adjusted by adding more or less water (by the tablespoon).
The activities should be all about testing builder skills. Give each child a bag of supplies and challenge them to build the strongest bridge or the highest tower.
Tie a ribbon to keys and hide them around the playroom or backyard (make sure they aren't too tough to find). Challenge children to find them. Once everyone has a key, the first child to find one can choose to keep his key or swap with another. Once his turn is over, his key is safe. You can only swap with children who found keys after you. Repeat until no swaps can be made. The children then try their keys in the locked box. The winner unlocks the prize. There should be a prize for everyone to share like a bag of lollypops, and an extra prize for the winner like a building supply.
Buy small, inexpensive tool boxes or hard hats from a dollar store and fill with building supplies and snacks for hard working builders.
Invite kids to come in work wear.