For DD(14) and DS(9), request meetings with their SENCOs at their schools. What support are the schools providing and what have they already tried that hasn’t worked? Request EHCNAs for the, both. On their website, IPSEA has a model letter you can use. Also request alternative provision for DD(14). Have they both been referred for diagnostic assessments?
Not all ICBs commission sensory OT on the NHS, but if your area does, it is worth referrals for DS(9) and DD(2). Do you have any sensory equipment? Will either of them wear ear defenders or noise cancelling headphones?
Does DD(2) go to nursery? Also request an EHCNA for her. Has a referral to SALT been made? If your area has Portage, also look at them.
Do any of them take anything to help with sleep?
Request social care assessments. A carer’s assessment for you and assessments of DC’s needs for them. On their website, Contact has model letters you can use. If you are refused, you can challenge the decision. There may not be anything suitable, but also have a look at your local short breaks offer.
If your area has Home Start, have a look at them too.
Do they all have their own bedrooms or do they share?
You need a buggy DD(2) cannot escape from.
How old is your other DC?