Congrats on your twins.

Carting 3 kids is pretty easy, we have a Commodore Station Wagon and a Hyundai Getz... Our DD is in a BabyLove Booster Combo Seat (goes from 6mths to 7 yrs). As it was going to be hard to get her buckled into the middle seat with the twins being in a rearward facing carseat we opted to hire 2 snap and go capsules until they were old enough to go into a forward facing carseats - it cost us about $200 for both for 6 mths.

The capsules are much easier with twins as you can load them into the capsules in the house and when we would be loading the car up, DD would go in first (I would put the twins near the back door) and then I would just take a twin at a time out and then load them up. It meant the twins were in a confined safe space as well while I was out of the house buckling another child in the car.

Now the twins are in forward facing seats, they are all in the Babylove Easy Combo Seats and they all fit across the back seat of the station wagon. We also have 3 smaller width seats on the back seat of our 2 door Hyundai Getz - yep a 2 door hatch.

As much as you would think you can do the 2 car thing there are times when you will need to take them all out together, so if you are looking at pram options as well... We have the Valco Trimode Twin (which is huge, cumbersome and expensive) with a toddler seat attachment, but I also have a twin stroller which I use much more as it is smaller, lighter and takes up much less room. As DD is to young to walk on her own (27mths) we bought a VeeBee Sk8board attachment which has different connectors and hooks onto strollers so DD uses that, worse case scenario is that she wants to sit in the stroller (or pram if I am using that) so in this case I have a baby carrier in the car as well so DD and one twin will be in the twin stroller/pram and I put the other twin in the front pack.

Going out with a toddler and twins does require planning but it can be done quite easily. If you have any other questions I'm more than happy to pass on any tips, although once you are further along I recommend you make contact with your local Multiple Birth Assocation as they are a great support and a good place to get ideas from mum's who have been there.