You've gotten great advice here! Definitely rent the hospital-grade pump! Anytime a woman is pumping INSTEAD of nursing, let along pumping for two babies, she needs the very best pump you can find. With twins you're facing a couple obstacles - not only does your wife need to make a lot of milk, but twins tend to be premature and a bit delayed, so they are harder to breastfeed at first. However, many women have done it, and many have even breastfeed their babies exclusively! Set your sights at a reasonable level - get through today, keep up the pumping, and keep trying to latch the babies - but just know that it is possible.