I've never stayed in the cabins, but you'll be very happy and safe at FW. It's not like camping at a backwoods campground.
There's night security in that the gate is manned. I don't know if anyone goes around the resort, but they don't do that at any Disney resorts.
You park right at your cabin. They have phones and air and heat. I'd guess there's an outside light, but not having stayed in one, I'm not sure.
There are a lot of free activities, including a trail, night time campfire, singalong, and movie, and a beach you can walk on. For a fee, you can canoe down the river, go horse riding, go on a hayride, or fish. There may be some other activities as well. I seem to recall tennis or volleyball or something, but I don't do those things.
The ressies are just like all the other Disney resorts. You'll have to pay a deposit when you book; how much depends on if you book through DC, CRO or WDW Travel. That will also dictate how far ahead of time you have to cancel, but I think the longest one is 60 days out, so you'd still have a while.