James,
2 AB400s and a Vagabond II. A lot will be available light to get walking/footprints shots and that bucolic stroll on the beach. It really depends on what the sun is doing when we get there. This week's weather has been bright, sunny and 95 degrees. The rest of the country might be waiting for Summer but it's been here for a while.
I'll scout the location later today at about the same time I'll be shooting and see what I need then. I've done similar shoots with just the 580 EX for fill but I've gotten some blown out highlights that way. Of course, I have no idea what they're wearing either so if I get white, I'm in trouble. Linda will be there to assist and help with the reflectors and other stuff.
If it's windy, it will be lots of fun

. Then I'll just take my chances with available light and the 580.
Jim