My daughter is 11 months old and she has been sailing on our boat since she was 2 weeks old. We bought two child pfd's last year at the boat show when my was pregnant. One is for under 30lbs and the other is for 30-50 lbs. Get a jacket that your child can wear.
We brought the car seat along with us on every trip. She liked to sleep in it which gave us a break from holding her. I would wedge it in the quarter birth so it would not move with heeling. We have been out in some big winds (20 kts +) and she has slept through most of it. When she is awake and was smaller we used the "Mini-Me" carrier so she could look around but who ever was holding her could quickly use their hands if needed.
Now that she is older she likes to be able to move around the cockpit. I think we will be looking to buy a harness this year.
As for provisioning, we breast feed ours so milk is not an issue. Baby food keeps without refrigeration so you are ok there. I have found dirty diapers to be our biggest problem. Definitely make sure you stop each day to get rid of them. Bring plenty of sets of baby clothes and lots of wipes.
For sleeping we have lined our V-berth with pillows so she can roll around and not hurt herself. My wife and I sleep in the salon. I was worried about being in crowded anchorages with a baby screaming in the middle of the night. Supposedly the other boats don't hear it, or they are just being nice to us.
With our daughter we have found that the more motion of the sea, the more likely she is to sleep while we are sailing. I guess it is very womb-like for her.
Best of luck