majorstres, Just do the clothes one step at a time ...
I know you feel guilty about taking time away from your dds to declutter. But it is very stressful to live in chaos and be reminded of it day-after-day. I suffer weeks of this when there is a birthday or christmas and the dcs get tons of toys and gifts which lie around my living room until I find the time to organise and put them away.
I use my social conscience to lubricate the dreadfully boring task of decluttering.
For clothes, block out a morning. Take everything out of drawers and closets.
One bag for clothes to be thrown away.
One bag for clothes to the charities that collect from your door - do you get this whereby you can put the clothes in a bag and leave it outside your door for them to collect? Granted it might be some company (rather than charity) selling to Eastern European people, it is still better than throwing into the tip. This lies around until the leaflet for the next charity collection comes around. In this bag, put all outgrown clothes, all clothes which are out-of-season and soon to be outgrown, in reasonable condition.
Another bag for nicer clothes of the above description. For these, I take them to Oxfam (who sell them in their charity shops) or sell on eBay. If you have designer clothes in good condition (Next, Monsoon, Gap, Boden), don't underestimate how much you can get for them on eBay. But it does take a bit of effort to sell on eBay.
What you are left with, organise into piles: Clothes in season - split into clothes for each dc. Clothes out of season - to be grown into - again split into clothes for each dc. Then put them into draws closets in this order.
I put all small items like socks, tights, hats, scarves, gloves into one drawer.
After every laundry, make sure you put away clothes in the system you have organised.
Going forward, you have to do this everytime you get a load of clothes. Hand-me-downs contain a lot of dross. You should not even put them in the drawers before sorting them out in the above system.
Now exhausted.