Used a white backdrop with the sun shooting through the back of it, used spot meter so the camera wouldn't try to underexpose the background. Opinions?
Very clever; you got an almost high-key shot without a single light! Minor niggles are the blown hair and slightly shadowed faces. If you'd used a big reflector, you would have nailed this. Good job.
No, we setup and started shooting I think about 2:30-3:00, that way the sun would not be shining straight down. What I did before we setup the backdrop is I stood and looked at my shadow, and wherever I saw my shadow is where I wanted the front part facing, so the back would be letting the sun shine straight in and not at an angle.
Two things I've learned to watch out for so far:
1: Try to get the wrinkles out of the backdrop, at least the big ones that cause shadows.
2: Wind can be a major problem, so I never raise the backdrop anymore than I have to, if the subject is a kid or laying down I lowered the backdrop enough to fill the frame and that's it.
Another shot the same day, this one I did a better job at not blowing out the hair so it will give you a better idea.