If you are doing short trips, why not just have him take non-dried food? The gal I hike with has gone to no-cook meals and makes her own bread and trail bars (gluten free, dairy free, vegan). She also takes fresh vegetables and avocado. Her pack is a bit heavier, but not that much for a 3-day trip. I cook for myself using lighter dry food and she does her non-dry food thing. I do not see why your son could not simply do his own meals. He probably can easily carry more weight.