I have six month old twins and DD1 who just turned three. I have been breastfeeding them since the beginning; DD2 does get one bottle a day of about 3oz EBM to help simplify the bedtime routine. I won't lie to you; it's hard having a toddler and newborn twins. Very hard. But it's not breastfeeding that makes it hard! In fact, I think nursing them made it easier because I have a guaranteed way to soothe them. Hungry? Tired? Cranky? Lonely? Bored? The answer is always boob! A bottlefeeding mama can't do that.
Then there's the health factor. Twins are more likely to be smaller, and to be premature. Breastfeeding is doubly important in those cases for the babies' health.
It can be hard getting started nursing a very small or early baby, but once you get past the initial difficulties I think breastfeeding is easier. Can you imagine having to pack bottles and formula for two every single time you go out anywhere, in addition to everything else you have to do?
Anyway, I think you should just make up your mind that you're going to do it no matter what, and it will all work out. Try and line up as much help as you can for the first six weeks or so, especially help with non-baby stuff like housecleaning or cooking-- you won't want to be bothered with those. Someone who can help keep your older child happy and entertained is a blessing, too; I think older siblings have the hardest time with twins in the house. But you can make it without help if you have no choice; I had very little help and while we had rough days, we managed.
As far as nursing them together or apart, I do both. I nurse on demand, so sometimes it's one and sometimes it's both. I tend to feed separately more often than tandem, though; I just find it easier. Positioning two has always been a challenge for me. Cosleeping has also saved us so much-- I slept for months with both babies, and just rolled back and forth and nursed in my sleep as needed. If I'd had to get up and get bottles, I never would have slept.
In the early weeks I felt like I did nothing but nurse, but now they've gotten more efficient so it really doesn't take all that much time at all.
I used my pump a lot, not to let Dad feed, but because DD2 had a weak suck at first, and DS had some nipple confusion issues due to idiot nurses in the hospital, so I needed the pump to keep up my supply while we straightened all that out. Now, I work part-time, so I need the pump for that. A double pump, if it's not out of your budget, is a blessing. It will stimulate your supply so much better and save you a pile of time. But you can wait until the babes arrive and you are sure you need it before you invest in it.
me , he , my three , , and -- and the one we lost