I led my scouts in building a PWD car stand. It had room for 5 cars (1 for each year) and could either stand on a surface or hang on a wall. Can't remember if I posted pics...I will if you're interested.
Back in the BSA Centennial year (2010) I served as a merit badge counselor for the re-introduced carpentry merit badge (issued only in 2010) which included the requirement for the scout to make an item using hand tools. I provided S2S poplar that was ripped to width and had the scouts cut out a small stool using dimensions that I provided. They were assembled with pocket screws and all the holes were drilled by the scouts with a brace & bit! They used an old Yankee screwdriver fitted with the square bit to drive the pocket screws (I purchased a Yankee hex bit holder online). All the cutting and drilling would be too difficult for 7-11 year old Cubs. FYI - the ends are secured to the top from below via 2 pocket holes on each end. For this design the 4 end pocket holes (end to top) are covered by the runners in the assembly process. Each runner has 3 pocket holes - a total of 14 pocket holes per stool. I made a jig for the boys to use for assembly to line up the parts.
Perhaps you could precut the pieces and have the boys drill one pocket hole with a brace & bit so they would have a new respect for power tools. You or a parent could drill the remaining holes with an electric drill. If the boys are Webloes age (10-11) I would think they could use a electric drill in the pocket jig with adult supervision. Incidentally, the highlight of the project was letting the scout brand his stool with a custom branding iron I ordered for the merit badge.
She told me today that they only have 45 minutes to finish the project. Kind of limits things. But keep the ideas flowing. I really like the pencil box - very simple - but has a secret compartment.
Thank everyone for the replies! Day camp is doing Bug Boxes (with screen), that should be cool, and we decided on Catapults. We're going to launch marshmallows at targets.
I thank everybody also for the ideas. She's not a member but has been watching this thread with interest. Guess she got some other ideas from other sources. Marshmallow catapults sound like fun also.