Child 16 in March, can I apply for DLA?

Child is suicidal and self harms, suspected ADHD and Autistic, currently under CAMHS, has weekly counselling and is about to be put on reduced timetable from school. I have the worlds best boss who, up til now has supported the numerous calls from school to collect child, time off to attend appointments and during hospitalisation for suicidal attempts. But it's now at the point it's really affecting my job and the business overall and I am absolutely exhausted from having 4 hours sleep each night due to being on suicide watch.

I called for DLA forms at the start of this year but never received them and hadn't given it any thought but now I'm at the point where it's highly likely I'll have to stop work.

Given that child will be 16 in March can I apply for DLA or will it have to be PIP. And if it is PIP would that attract the disabled child element of UC? Can you even get PIP for this situation? I have 4 children at home and rent is £1295 pcm so being benefit capped would cripple us