Sing that's sweet of your son to decide to donate.
I've done it with the junk cupboard. After 3yrs of living here I finally sorted it out a few months ago. It's now a home for specific things, all organised into different areas by type and anything that's actual junk is gone. One little cupboard but it felt like the biggest deal ever to tackle that. I'm trying really hard to not have any 'I don't know' piles. Post is filed, shredded or recycled same day now, I've got a file of things that need doing so nothing left hanging around. Items that come in and don't have a home are found a home right away. I find once that 'I don't know' or 'I'll deal with it later' pile starts up it quickly gets out of control and becomes a mammoth job to sort out even when it's still small. Plus it looks so messy I can't stand it. I've changed my mindset from doing the big things and fitting the little things in when there's time to ensuring all the little things are kept on top of and only working on the big things after. I've found its better this way round because it's tidier so I'm less stressed and so more likely to do the big things.
Elleherd you've done amazingly well.
Chillied you can't live your mother's life for her so don't feel guilty if she adds to her hoard. Her behaviour is not your responsibility.
But, those books belong to you now not your mother. Do what you think is best with them. If you don't think it's best to offer them to your mother or to tell her you're getting rid of them, then don't. You don't need her permission, they're your books.
If you want the memories take a photo of the collection and when you've got a few of these 'memories from childhood' pics of various objects, either print them out and put them in an album or scrapbook or keep in a digital file all together. You don't need the actual items to have the warm fuzzy feeling from the memories. The books can go to charity shop or be sold, someone would love them for their little one.
Down overalls is a good idea.
Today I've finally finished up an enormous bottle of shampoo 5L so that's going outside to recycling and I'm celebrating it no longer hanging around in my kitchen. Small successes!