Outdoor family portrait - Could use suggestions

So I've been planning to do this family portrait for some friends of mine. This is a family of four that couldn't be more white/blond. I was planning to shoot them in my studio with darker backgrounds, but they just threw me a curve and said they'd kind of like it done outside. With very little experience at this sort of thing, I'm looking for suggestions.

I have one 580EX flash with a PC port so I can use it off camera if I want. I can use this flash with my 22" Kacey beauty dish or 24"x24" Lastolite Ezybox and PWs off camera. I also have the Lumiquest ProMax System and large softbox that attach directly to the flash on camera. I have a couple of reflectors I can use as well. I'm not even against the idea of picking up a second speedlight. I've been looking for an excuse. But if I can do something nice with what I have, all the better.

I think I'll have some flexibility about time of day and setting. So I won't be forced to do this in direct sunlight at noon or anything like that. They're probably going to ask me how I want to do it. Since I'm used to being able to control everything in the studio, all suggestions for this type of shot are welcome!

I though you had studio lights? I will pick some battery power for them or someplace where power outlet is available, like in their backyard.

Regarding hot shoe flash option, look at this guy's shot. I think they turned out pretty well.

https://photography-on-the.net/forum/showthre​ad.php?t=754422

if you have an assistant, use a reflector instead.

bobbyz wrote in post #8719075
I though you had studio lights? I will pick some battery power for them or someplace where power outlet is available, like in their backyard.

Regarding hot shoe flash option, look at this guy's shot. I think they turned out pretty well.

https://photography-on-the.net/forum/showthre​ad.php?t=754422

Those are great shots. I'd be happy with something similar, and it seems like I should be able to do it with equipment I have. I don't have a shoot-thru umbrella, but I would think a softbox would give me something similar. I guess it's an option to use my studio lights outside, but I wasn't planning on that. I was thinking "strobist" and reflectors for this.

How big is the octa?

Look at the first pic in bobbyz's callout. Dad got punked on the light -- he's measurably darker and features harder shadows. Why? Cause hes farther from the light, which makes it harder as its apparent size is smaller. Its not a bad pic, but the effect is noticeable if you are looking.

With a family of 4, you can group them tighter. But to account for the falloff (remember, light closer in falls off faster) you're gonna need a big source to get something nice and soft, while getting it farther away to control the fall.

Or try something nutty, like a white bedsheet as a reflector. Doesn't get much bigger than that - at least not for 5 bucks.

mattograph wrote in post #8724428
Or try something nutty, like a white bedsheet as a reflector. Doesn't get much bigger than that - at least not for 5 bucks.

Sorry to hijack OP's thread but how to hold/mount the bed sheet and that too outside and god forbid if it is a bit windy. Would be nice to know the little details for us rookies.

One thing very important to take note of in these example shots linked to here is that there is no direct sunlight hitting anywhere in the shot. It is all open shade. This is not always easy to find, but when you can, and the setting is great like in these shots, then you are golden. All you need is a little directional light from an added light source like done here so it is not flat and you are good to go.

If you run into a setting where there will be a higher dynamic range of light because there is direct sunlight hitting anywhere in the shot then you will have to try and balance the artificial light power with the sunlight, a much trickier scenario, especially with one light, but it can be done.

bobbyz wrote in post #8726095
Sorry to hijack OP's thread but how to hold/mount the bed sheet and that too outside and god forbid if it is a bit windy. Would be nice to know the little details for us rookies.

Only way to do it either put it on a frame, or have someone hold it. (two people.) You might able to stake it between two pieces of rebar.

I am getting a little out there.....

Well, assuming I can find a spot with no direct sunlight and want to setup a single directional light, the easiest thing for me to do is use the 580EX off-camera with a modifier I already have with hotshoe adapters, like the 22" beauty dish or 24"x24" Ezybox softbox. While not very big light sources, I could use a reflector to bounce some of the light back for fill. Is this worth considering, or should I instead plan on dragging a strobe outside with a bigger modifier, like the Photoflex 5' octa or 39" Elinchom deep octa?