John - are you still looking at red flowers for the hummers? I just started some Hibiscus Coccineus AKA Swamp Hibiscus - both the Texas Red Star and Texas White Star - and have been quite happy with them (have them sitting in a child's wading pool). You can start them by seed (I got 95%+ germination), they're perennials, happy in full sun to part shade, and they're hardy down to zone 6a.... just a thought if you are wanting something tall that will come back year after year.
That's going to be a great looking island!
