I have no experience with solar power chargers, but I've read that they usually take forever to charge and are heavy. Usually regular power banks are more efficient per weight (and cheaper).

There are plenty of sturdy USB power banks, and since you have time, look at amazon reviews. Anker has many options and sizes and they have worked for me. mAh*0.8 is max how much power you can expect to get to the phone/tablet. So typically a small 6000mAh will charge 1,5-2 phones. Bigger 10000 or 20000 will last a lot longer, but also weight more. Since you are sharing I would use 10k as the minimum to take.

I like to have a faster charger and power bank, just because you can. Here's a rather well priced large capacity Anker it weighs a pound, but there are smaller ones available.

Because the camera uses manufacturer specific battery, you really can't charge them safely on the road. So you just have to get more batteries for it, but luckily they're a good investment since you have a really nice but not brand new camera. Here's third party battery for $10 shipped

Edit: maybe look at some other batteries for the camera, the ones I linked didn't have that good reviews, but there are plenty of third party manufacturers. The originals cost $50 which is ridiculous for a battery