You rang?
The key is colour identification, having a colour chart is useful for distinguishing between brown and reddish brown or light grey vs medium stone grey.
If not by colour keeping mould types seperate. For example these are 4 distinct variations of the same part.
All in easy to find labelled organisers.
Obviously you want to keep the kids as far away from it as possible, it’s not a toy 🙂
Seriously though for kids a few big boxes you can rummage through to find bits, to be honest I still build like that now, usually a big pile of random (usually grey) bits. If you want to be slightly more organised (and unless you love sorting the stuff you don’t) sperate by type, eg plates in one box, bricks in another, people and bits in a third but to be honest you’ll just spend all your time sorting it.