This is a generic list of items needed for most Eagle projects. Your project may vary, but the goal is to not forget anything major by having a list to pull from.
Pen and paper for the sign-in/sign-out sheet; record name, time in, time out
where is the bathroom
plaque for the end of the project, identifying the Eagle and when the project was done
first aid kit
Eye protection (glasses or safety glasses), ear protection (foam plugs, ear muffs, etc), gloves, knee pads if kneeling on rough surfaces, n95 masks if sawdust,
sharpie marker for general purpose marking stuff; pencil for marking measurements on wood
sun protection: hats, sunscreen (especially nose and tops of ears), sunglasses, bandana for back of the neck; canopy for shade or identify where tree shade will be at each time of day
Reusable water bottles, water in a cooler with ice, cups for those who forgot their bottle;
hand sanitizer, plates, napkins, cutlery (if needed), snacks, lunch (check for dietary restrictions; easy options include pizza, catered sandwiches like jersey mikes and subway)
trash can and recycling available? or bring two bags
tools needed for the project, including enough duplicates to enable teams to work simultaneously; generator for power tools, or fully-charged batteries, tape measures, short and long levels, hammers (including sledgehammers for some projects), saws, screwdrivers, utility knife, enough shovels for everyone on the team, enough picks for enough members of the team; table for stuff; sawhorses, broom to clean up dirt/shavings/sawdust; folding saw to cut tree roots
Keep each scout engaged, give them a job to do; assign someone to pick up trash, sweep the worksite, get the food, refill the water, keep shovels/rakes turned to not be hazards