I agree with Jason. Everyone needs to be cautious at mealtime. One of the most difficult things to eat out of will be the tuna pouch. If you're not careful, it will be on your shirt or pants quickly. However, you can always purchase these and practice on one of your shakedown hikes. Your crew should be looking over the 2011 meal choices now so they can get an idea of what to expect.
Your layering system seems appropriate. Remember, the sleeping clothing you choose can always be used as part of your layering system if you become cold while in the backcountry. A wind shirt like a GoLite Wisp or Montane Featherlite Smock is a great addition that will give you plenty of versatility with your hiking shirt, insulating layer, and rain coat.
Without knowing your trek # and which week you will be at Philmont, it is difficult to know what weather you may encounter. From mid-July into August you can expect more rain.