I went last year and used the Vasque breeze model you have without goretex. If your boots work, and fit great use them. I practiced walked on our sledding hill using 27#'s of charcoal in my pack. I think using your pack with weight is all you need to practice, since you are in good shape. If you are planning on using poles, practice with them.
Gear. We bought an Oware 12'x 12' sil nylon tarp, and it was worth the money, about $150. We had somehwat rainy trip, and this tarp was pure gold. We used our hiking poles to set it up. Practice was key prior, as we could rig it in a number of ways, and had precut ropes we brought along, with pole connectors also. Best thing we purchased. Way lighter than theirs. If you use white gas stoves, make every effort if possible to buy good known gas prior to arrival. We used theirs, (had to, flew into denver, then bus to philmont)and stove performance sucked, and it wasn't the stoves. Have a gear shake down now. Get the parents to spend money where possible on lighter weight, smaller gear. Sleeping bags are prime target, followed by rain gear, sleeping pads, and packs for big weight savings. Packs for size. Too small a pack = problems with boys carrying their share of equipment and meals. That leads to other problems, lol. Campmor brand 20 degree down bags are a great choice for small, light, and relatively low purchase price. Your troop should get 10% discount there also if you set up account. Good luck