I've had three kids (18, 8, 3) via c-section, and after the last one the nurses put it on me as part of the normal post-op procedure. Holy mackerel, it felt SO much better! I was surprised at how much difference I felt when I removed it for showers, etc.
But definitely, it will do NOTHING for your skin. Stretch marks and skin resiliency is purely a function of genetics - you either will or will not snap back, and no amount of creams, exercise or even the support garment will change the outcome.
However your body reacted after your son's birth is the best predictor for your reaction this time around (accounting for a second pregnancy and being just a little bit older!).
Best of luck, and enjoy the babies!