Jeremy,

You sound like you are in good shape, enthusiastic, and experienced in the outdoors. So you should be able to handle just about any gear; weight isn't going to be a huge concern right now. And when you start hiking with a young child, you end up being a serious pack mule for gear. I remember carrying 65+ pounds when we started backpacking with our then 4-year old daughter. Part of that was owning heavy gear, and part was "OMG we are taking a four year old into a wilderness area!"

Your list of gear is comprehensive. You are leaning toward heavier traditional gear -- heavy hiking boots, a very large pack, 3.5 season tent, etc. Not that there's anything wrong with that, but this forum is populated by hikers who (mostly) value light weight, so just be aware that that's the direction we tend to lean in most of the time.

My advice would be to keep the winter gear separate. You may want a heavy winter tent for winter use, but you'll likely be unhappy carrying it in July. Same with sleeping bags -- you'll want two, one for April - September, and one for October - March, or thereabouts. Same with heavy boots. You are a trail runner -- wear your trail running shoes in summer, at least. You'd be surprised how much support they will give you, and you already know the comfort level. Buy the winter snowshoeing boots when you are ready to go snowshoeing.

You asked for some specific recommendations, so here goes:

Headlamp: any light LED headlamp that takes three AAA batteries. I happen to like the Petzl Zipka.
Trekking Poles: the WallyMart specials are fine.
Filter: The Pur Hiker is simple and works well, and it's what I use for family hikes. For solo hikes, I use Aqua Mira.
Stove: Plenty of choices here. Don't spend a lot of money -- a simple stove and an aluminum pot will do for now. Save the Titanium and the superlight stoves for later. (Realize that I have a bunch of titanium and superlight stoves in my gear closet.)

Clothing is a whole separate subject. It could be a book. Again, your winter clothing is mostly different. You can probably start three-season hiking right now with stuff already in your closet. Synthetic shorts or zipoffs, a synthetic t-shirt, wool or synthetic socks, a fleece pullover, a rain shell and maybe rain pants would be a good start. When you take your son, don't skimp on his clothing. My experience trying to "cheap out" with kids clothing and especially rain gear was not good.

Great advice to check the various packing lists on this site. Good luck and happy trails.