Best slings/carriers for preemies?

I haven't really thought this through much.

I'm on my fourth pregnancy and I'm highly likely to have a preemie (consultants have said they are attempting to keep this one in till 28 weeks)

I've had 24 weekers and a 27 weeker.

My youngest is extremely disabled and 14 months. She requires a pushchair wheelchair for hip, chest, feet and head support.

I'll need to do the school run for my 2 oldest children.

I'll need to take baby and my disabled child so double buggies etc aren't suitable due to her complex needs.

Anyone recommend a sling or carrier?