As far as discounts at the parks/ Downtown Disney when using the Visa card, we used our Rewards Cards (not the credit cards) and showed our Visa and still obtained the discount. We also paid the rest in cash at World of Disney and showed the card and still received the discount. This was at WDW, but I will try it again at DLR in August.
I do not know if this is policy or if we were lucky, but it is worth a try.
