Leave it or take it, rent it or buy it?

WHILE viewing the next to final episode of “Sex and the City,” I teared up. Not because I cared about the fate of the characters but because it illuminated so clearly the neat halves into which my traveling life was hacked by childbirth.

Carrie is going to Paris, and all she can think of is how many pairs of shoes (and, as it turned out, feathered ball gowns) she can get on the plane.

Me, I’m not going to Paris any time soon and even if I were, I’d be spending that precious hour before departure making sure that the Neosporin in the first-aid kit hadn’t dried out, that we actually have taken the tickets out from the top-secret hiding place where we put them so they would not be scissored into snowflakes and that there is at least one packet of diaper wipes in every piece of luggage we have.

I don’t think Carrie had even one packet of diaper wipes. This is a mistake; diaper wipes are multifunctional — useful in removing makeup, shining shoes, freshening hands and face and getting pesky spots out of wool. All with a baby-fresh scent. From the moment you take your newborn on his or her first 20-minute car trip, travel becomes less about movement and more about stuff. The byproducts of digestion are a big problem. Although this improves with time, as my pediatrician once said, even older kids vomit a lot.

My kids are way past the diaper/porta-crib stage, but I never go anywhere without a backpack that contains a change of clothes for each, a medical kit, crayons, a kitchen towel, at least one kind of snack and, of course, diaper wipes.

“We’re just going to the zoo,” my husband lamented recently. “Do we need to take that whole thing?” Well, yes, as it turned out because when Fiona spills her milk she means business and I’m not shelling out $14 for a zoo T-shirt when she has 7,000 T-shirts at home.

On the other hand, did I need to take 10 days’ worth of diapers to Ireland, where there are probably more babies per square inch than any other place on the planet? No, I did not.

To pack correctly for a family vacation, you need to think like a quartermaster crossed with an accountant. What am I willing to buy during the trip, and how much time am I willing to spend looking for it in order to avoid carrying it? Diapers are a prime example — no doubt there are places where disposable diapers are not readily available, but are you going to take your child there for vacation? Unless your child has had bad reactions to different brands of diapers, pack enough for the plane/car ride and a day or so (stores are not always open on Sundays) and then live like a native.

But I don’t want to spend my vacation poring over the ingredients in over-the-counter cold medicines (like I would know what they were anyway), so if we’re going out of the country, I always pack plenty of Pediacare and Children’s Motrin.

Here are some other things to consider.

• Car seats: After taking and renting, I vote rent, even if it seems pricey. When trying to get through Dublin airport while balancing two car seats, I would have paid hundreds of dollars to have had them taken off my hands. But do ask what sort of car seat you are renting — the one we got in Vatican City was made mostly of Styrofoam. “Did you get this at Burger King?” my brother asked.

• Stroller: Always take the stroller. Even big kids get tired of walking, and 20 minutes of being pushed can reinvigorate a 5- or 6-year-old child. That said, I am still seeking the perfect travel stroller. Umbrella strollers with hard wheels are useless in many European cities because of the cobblestone. We took a jogging stroller to Italy, but it was large and unwieldy. Now we have a quasi-umbrella stroller with soft “off-road” wheels and that seems to work.

• Porta-cribs: They seem like a great idea, but they are heavy and hard to set up. Most hotels and rental houses have cribs available.

We had been known just to pull a spare mattress onto the floor when our children were really little. For kids old enough for a bed but young enough to fall out, take a portable bed rail or two, which fit nicely at the bottom of a suitcase.

• Baby backpacks: If your kids are small enough to fit into a backpack, this is the way to go. Get a good one though, with a real waist belt for added back support, and a frame that stands on its own so you can put it down safely when the child is asleep.

• Kitchen towels: Messes of all sorts happen with alarming frequency, and kitchen towels are big enough to cope with most of them but small enough to be wrung out in a gas station restroom. They also dry fast. Take as many as there are children.

• Spare clothes: On the plane or day-tripping, a change of clothes for the kids goes without saying, but too often I forget to take a spare shirt for myself and my husband. Which is strange considering that most messes, though originating with the child, wind up on the adult.

• Ziplock bags and other handy items: The bags take up virtually no room and solve an array of problems. Other handy items: a roll of toilet paper, adhesive tape and disposable cameras (you don’t want the real one to end up in the Danube).

• Snacks: Always carry food. Your children will inevitably announce their desperate, immediate need for food three minutes after you have paid $25 for the family to tour the cathedral.

• Toys: Don’t take anything you can’t afford to replace, either financially or emotionally.

• An extra bag: Pack an extra bag for all the stuff you accumulate during your travels. I never do, and I always wish I had because I am too cheap to buy one and wind up shoving seven bulging plastic bags together and trying to pretend they are one carry-on. Embarrassing.

And don’t forget the diaper wipes.