By the way, the first aid kit should definitely include a blister kit. At least one person should carry a trail description and the applicable topo map, plus a compass. Everyone needs a dependable fire-starting device, typically a butane lighter or a container of waterproof matches. Each person needs a dependable headlamp or flashlight, as well as a candle. Bring a couple of heavy duty plastic trash bags.
Someone needs to carry the necessary cordage with which to suspend the food bags.
A length of duct tape wrapped around a water bottle, a hiking staff, or your pack frame will probably come in handy. I carry a wooden hiking staff. On most trails, though, you're probably just as well off not having to carry anything in your hands.