Hi Jennifer
Both of our children started caravanning at around 3 months old.
The main thing that we were concerned about was noise really. Both from the neighbours of an evening when the kids were trying to sleep, and from the kids in the small hours when they get their own back. We therefore tended to be a bit unsociable for a while, and parked up away from the centre of activity. This did seem to work as I don't remember them being woken up, and no one complained about any crying in the night.
I did a bit of improvising for the cot. I used two quick fit shower curtain rails. This is the sort that you can fit between two walls in a bathroom without drilling holes. They're telescopic, and work by extending them until they're hard against the walls, and then twisting them to lock them. We already had one kicking around, and so purchased another. We then got some old net curtain and sewed around them both, like a stretcher, so there was about 60cms of material between them. This was then very simple to fit to the bed in the evening, and remove and store the next morning. Anti-slip matting gave the ends added grip. It must have been strong enough as it was never pulled off by either of them. When they were older, we changed it to a portable bed guard that could fold up during the day.
Keep a good supply of nappy bags in the caravan and car. If you have a dog then these are also great for clearing up after them. We still use them now as they're alot cheaper than poop bags that you get in pet shops, and smell nicer as well. Well, when they're empty that is.
Food wise we just had a small electrical food warmer, it came with a dish on top. My wife made a lot of baby food herself in a blender, which was then frozen and taken in the ice box of the fridge. Milk was never a problem as Mum supplied it all.
One really useful bit of kit that we had that's a bit difficult to describe, is a child seat that could be used on a normal chair, or clipped onto a frame and attached to a table. It is made of plastic and can be adjusted to two heights when attached to a chair with straps. Or it can be clipped into a metal frame which then clips onto a table. In our Bailey the table wasn't free standing, one end attached to the wall and the other was supported by a single leg. This was ideal, as the chair frame easily clipped onto the leg end and wasn't going to tip up as the other end was secured to the wall. It also came with it's own detachable tray. This meant that we could all sit around the table together without any problems and with plenty of room.
Take a night light, especially if you have a socket in the sleeping area that can be left on safely at night.
Take plenty of the favouite soft toys and blankets to help them to sleep.
A backpack child carrier, or front carrier is also more practical than a push chair or pram. You can still go wherever you want to, shopping, walking visiting places of interest etc very easily, and it stores easily in the car. It also keeps you fit.
We found that the rear wash room of the caravan was a boon. If the baby/child has an accident, no messing about, straight in the shower. Take the clothes off in there and give them a quick shower straight away. Easy.
Take plenty of packs of baby wipes. A pack in the caravan, one in the car, one in the backpack etc. They're also great for cleaning your own hands after a meal for example, or even getting marks off clothes or furniture. We still carry them around with us now, years later.
Take loads of nursery rhyme or story tapes or CDs in the car. It can help a long journey to pass without too much whining.
The main thing is though to keep them interested. Wildlife parks are great and sets the childs interests for the future. Our kids are now 6 & 9, and last week when we went away they were allowed to stay up late each night to watch Springwatch on the BBC with Bill Oddie, Kate Humble and Simon King. They love it. The kid are now wildlife mad. Plenty of outdoor fresh air, yes I know that it's unavoidable in a caravan, and they'll be asleep in no time. They'll also grow up to love the great outdoors.
As long as you can put up with the "I want" every time you pass within sight of a gift shop, you'll have no problems and happy campers.
I'm sure that I thought of something else earlier but can't remember it now. Oh well, may have to add some more later.