But, there's a big question: are they driving to some location and camping near there, say within a mile? Or, are they parking and hiking around for 10 straight days. If the former, there are all sorts of things that can be thought of as luxuries to have on such a trip. If the latter, then can we assume they're experienced backpackers? If so, it'll be hard to think of something they don't already have - weight is a significant factor for anything they bring. On a 10 day backpacking trip, every pound counts. So, while it'll be difficult to think of something they don't have (if they're experienced), you might have to settle for a big improvement to the quality of something they already do have. As mentioned, the higher end flashlights are a possibility.
btw: to the cell phone charger via battery powered device suggestion: Use Google maps to see where Churchill MB is. I doubt that Churchill even has cellular service.
Hey, I've got a suggestion: they make these new bug repellents that are kinda like the old candy necklaces - you put them around your wrist or ankles. Supposedly 1 on your wrist is enough to keep mosquitos off you. When I was camping 2 weeks ago, my nieces had them - I was amazed that they actually worked quite well. You might want to get them some to try. They're quite lightweight. I have no clue about brand or anything else; I was spraying myself like mad to keep the mosquitos from carrying me away while I was fishing at night... they didn't need spray at all.