Early Dinning is mostly from 5-6 on area rest. Many stop the dinning at 5:45. I have seen people come in a few minutes late and be refused the early dinning menu. There is no coupon needed. The Island dinning guide that you get at checkin will list pleanty of places that offer early dinning. I think it is around 50 places. each place has their own prices, offerings, and times.
If I had to choose between Alexander's and Red fish, personally I would choose Alexanders. We love to sit on the patio and the food is great. There is atleast 6 items or more to choose from on the EB. Red Fish is great, too, but at the beach, we like to sit on patios. Red fish is a darker romantic type place, though it can be very loud if it is busy. Alexanders is classic American steak and seafood, RedFish is American,Cuban,Asian fusion type cuisine. Both are good, so it is just you are more in the mood of.
IF you want the patio at Alexanders, you need to ask for it, or they will seat you inside. it is a covered screen porch, so it is open even it is raining.