Not sure I'm in a position to advise, as our house is full to the brim, and dcs' bedrooms in particular, are a tip
but
I think trying to deal with things as they come in helps, and having 'systems' and it would help if your dh thought the same - that's where my plan falls down.
So, for example, when the post comes in, I open the envelope, throw it away, throw away the leaflets, read the letter and either throw or shred that, or put it on my pile to take upstairs (where filing cabinet and computer are). dh, OTOH, will open it (say it's a bank statement) then put it on the side, with the envelope, with the leaflets, etc, and even leave it on a pile if it's junk mail. Little things but they add up.
Same with letters from school / cubs / dance / swimming / etc. - I've got a folder for each child. I read the letter - if it's a form that has to go back I fill it in then and put it in their scouts shirt pocket so it's not forgotten next week / school bag for next day. I put it on the calendar then and I file it in their folder, as I might need details from it when the camp/event is imminent.
With their clothes - I leave them to put their own clothes away - if they don't, it's them that looks crumpled, not me. Make it easy though, by having plastic boxes under the bed - say one for all you'd need to go to football training (boots, training top, kit, shin pads, base layers, gloves, etc), all the stuff they need for Scout camps, (roll mat, torch, warm hats, camp crockery and cutlery, etc.) lives in the bag they take to camp, on top of the wardrobe.
I agree about not having too many toys 'out' - put some stuff in the loft / garage and limit what's in their rooms or your living room - they then love the stuff when you get it out the loft in 6 months time.
At mealtimes, teach them all to clear their space + one other thing as they leave the table - straight into the dishwasher, and something shared also to be put away by them. It's not then a big job for one person to 'clear up' after meals - most is done.
Put stuff on stairs to go up and teach them to take something with them - this is hard work and involves lots of making them come back down and take stuff they've left, but is worth persevering with.
Sorry
long post!
I think what I am saying is do as much as you can - and teach them to - so that they don't become a 'job', it's just 'as you are passing' stuff.