I agree, 7:30 would be the best time. We used to make ADRs for 5pm (watching the sunset is great to watch from up there too), but then we were able to score a 7:30 ADR and was able to watch Wishes right from our table. Now, that is what we make each time we go.
I am also watching for when bookings will open up, we will be there in October and DH loves this restaurant (as do I) and he would love to eat there, and I would love to surprise him with an ADR.