It's the good standard itinerary, still too fast in my opinion. If you can add one extra day, I would also spend it visiting Ama Dablam base camp, either sleeping in Upper pangboche or the lodge there (it was closed in Dec).
If the weather is clear, I would just drop my bags in gorak shep and then directly go to Kala Patthar on the first day up there, there is more than enough time. I love sunset from Kala Patthar as the light is really good (in morning, sun rise just in front of Everest), plus you also have the best day light on the way up compared with the morning. Obviously, then you don't have to wake up super early for sunrise as it's damn cold there, especially if you want to spend time for shooting.
Good that you have an extra day in Gokyo, but note that lakes will be frozen, thus a bit less scenic.
For charging your batteries, it's no problem but "somewhat" expensive (up to 500 rupees for a charge), but it will be low season and you can negotiate to include a charge in the night price.
If you need wifi, you can buy a 10gb everest link card in Namche that can be used in lots of lodges all over your itinerary (even Chukung), very usefull.
