I've got twin girls who are now 4 along with a 6 yr. old boy. No matter all the crazy stuff, you eventually get use to it. Feedings take a bit longer at night, but you adjust quickly, diaper changing becomes like a pit stop and you find yourself timing how fast you get the two changed, or in my case 3 for a while.
The best part is they'll always have a play buddy and you'll find them entertaining each other in no time. Big sister will not only gain two playmates down the road, she'll also be view as royalty for the most part by the twins.