I had a postnatal doula after I had my second child by c-section and she was fantastic. I purposely chose to have a doula rather than a maternity nurse as most mn's I have met are incredibly precious about doing anything apart from looking after the newborn and certainly won't tidy up your house or look after your toddler.
Nanny would look after the older kids & get their food & do their washing but wouldn't do any housework. And not all nannies have newborn experience so you'd have to look for the right one.
My doula came 8-12am every day. She made/changed beds, put on the washing, hung up the washing, did the ironing, swept the floors, loaded/emptied the dishwasher, made me tea, played with toddler, took toddler & baby to park while I slept, looked after baby while I went out, looked after both while I went to dentist etc etc etc. She also provided a sympathetic ear and had loads of experience with newborns. I didn't need that much reassurance about the baby as it was my second but how I wish I had had her first time round when I was a neurotic nutter with low-level PND.
She came for 6 weeks...ended up staying 10...I was gutted when we had to say goodbye. I would recommend a doula to anyone. It just got me through those hard early days with a newborn - she was great company, the house wasn't descending into total chaos, and gave my days a sense of routine - even when I'd had a shocking night at least I knew there'd be a friendly adult face at 8am (my husband goes to work at 6am so I wanted her to come early).
I found her on the website Pupuce recommended.