Your sleeping bag worries me. Coleman bags are OK for car camping, but they are rather bulky and heavy for backpacking, relative to their warmth. What model of their bag will you carry? I looked at the Coleman web page and all their current models have more fill weight (much lighter than total weight) than the 850 g you have listed for your bag. The most important thing is will it be warm enough for the conditions you will encounter on your hike. I am sure you can get a lighter, warmer, less bulky bag, but guess what? It will be a lot more expensive! Carry what you have and if you like the outdoors, make a really good bag a high priority for a future purchase. You won't regret it.

Four of you ought to be able to share onr cook set and stove just fine, for more weight saving.

To follow up on another suggestion, there are bags that convert from single to double. They do come in handy.