When my twins were born I had a 2 year old and 4 year old. I also can't imagine the twin carriers working well, especially not past the 4-6 week mark. The best scenario was a double stroller and a regular carrier. My 4 year old mainly walked. 2 year old switched in and out of the stroller and I could pop a baby in and out of the carrier as necessary. I could also carry one baby on my hip when the other was in the carrier. When the twins were old enough to carry on my back, that was the best because I really could have my hands free without the baby restricting me in the front. My 2 year old was quite easy-going and independent so she ditched the stroller quite young and then I was even able to go out with just a carrier and a single stroller.
DS - 10
DD - 8
Twin Girls - 6