For the school work done by your son, try to purge some of it. You could scan/photograph some of the artwork and then throw out the originals. You could use some of the artwork to send a note or letter. And you can ask him what he wants to keep - if he has kids he might like to show them what he did when he was little.

A friend had a quilt made from special clothing worn by her kids (she sent it to a place she found on the internet - she doesn't sew). She had one made for herself and one for each of her kids. She used her son's old concert T-shirts for his. I plan to do this with the special clothing I am saving from my kids.

Label each bin with a number (Sharpie pen - number all sides and top) and keep an index of what is in each bin (in a plastic sleeve on the inside door/wall of the attic and a copy where you keep home information). This will make it easier when you are looking for something and will have to just tell your DH to get Bin #14 instead of looking through each bin.

Good luck!

Something that helps me when I'm going through the more sentimental items is to think of it in terms of others. I absolutely adored some of my chidren's baby clothes, bankets, etc., but I also know a few things about them.
-I have pictures of my kids with those things (and they are things.)
-I really don't want to lug all of this stuff around every time I move.
-There is a good chance the kids won't want all of it in their home when they move away.
-Things become outdated. I could hang on to all of this stuff and eventually discard piles of it in the future when I get tired of it, but then it would be outdated and no one would want to use it. If I donate it/garage sale it now, another child will benefit. And I will benefit by having extra room.

I would suggest looking at things like the uniforms/clothes and think about whether they would be useful to another child. For instance, another little boy could probably use the cub scout uniform. I would keep the badges and maybe the neck kerchief and donate the shirt and pants.

The books - go through them again. Are you ever going to have shelves to store them? If not, go through and rank them - favorite to least favorite and irreplacible. Keep the favorites and irreplacibles. Borrow the others at the library if you get interested enough to read them enough again.

Good luck!