The online depth of field calculators are a huge help.
I usually shoot less open with more people in the frame. Also a slightly wider angle helps with the dof anyhow and you want to use wider angles with more people. Sweet spot usually being f/3.2 or so fo full body on a 35 prime lens for me...
You could also try shooting on a mirrorless (or via liveview on a dslr) and have the strap around your neck with your arms extended outward to create a brace of sorts. Works great for low light shots for me. Shorten the neck strap so your arms don't have to extend so far out.
I prefer as much distance as possible, maybe 15ft or so. That way you can stop down a bit and still get the background slightly bokeh if needed. I usually shoot portraits in studio around f/8 or so.