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Brea -- I don't want to sound like a big know it all, but I have taken a few event photos, and know what you are up against here. My approach may not be the one you or others would choose, but I'll give you my view on how I'd make these shots more satisfying or successful.
My first advice for posed event portraits is to use a smaller aperture. You are shooting wide open with telephoto -- this give extremely shallow DOF, and even the single subjects will have some areas in focus, and some out -- too hard to choose unless you are selecting a specific feature you want to be in precise focus, such as eyes.
Second, when possible use a lens with wider angle for greater DOF. I like the 24-70L, and shoot most of these types of shots at 45-70mm at f/4.5 to 5.6 to assure what I consider adequate DOF for individuals and small groups.
If you want the effect on background of OOF or bokeh, you are going to have to live with a lot of slightly OOF areas within your subject area too. That's a creative vs. practical choice.
Regarding your specific pictures:
#1 -- I see many sharp elements, ruling out camera motion (plus you have high shutter speed). The fingers, parts of the hair in bangs and right side, fabric at waist area. But face seems a little soft -- just outside of plane of focus. I don't think you could do better at 70mm f/2.8 unless you stage the shot and use a tripod for precision -- that would not be "event style" but studio style. Otherwise trust to luck and shoot a ton to choose from. You are close to what you want here.
#2 -- Too many planes of focus! I know they look to be on the same plane, but even a couple inches difference will make you choose one subject or the other to be in focus and the other not, or in this case, neither exactly in focus. I know you used the smaller f/5, but it isn't quite enough for this much of a close-up. Use flash, maybe slightly smaller f/stop and back up a step (and crop later in PP), and balance your exposure to include the ambient light, albeit at a slightly reduced level. Or live with this result and use wider focal length, take tons of shots, and pray one will have all your key elements in focus. Flash would have helped put a twinkle in the subject's eyes too.
#3 -- I can't tell where the exact focus is in this one, but it does seem a bit off. It looks like her face may be just behind the plane of focus, but hard to tell. I'd need to see it at 100% to find the details establishing plane of focus.
The good news is, you've kept motion blur to a minimum by using a fast shutter speed. The flip side is you've had to open the lens all the way and gotten too thin a DOF. My usual is to go for lower ISO (1600-3200), flash/flash fill, 1/50, f/5.0, 24-70mm. Perhaps some others can give advice for posed shots with telephoto, high ISO and available light -- I've just found it too risky for paid assignments. People want to "look good" meaning good color and sharpness, unless it is a performance or activity.
Note: using flash would have helped get rid of the (sodium vapor?) color balance on the subjects! Best results are to filter the flash (if possible) to match the ambient light, then use the flash to balance or slightly subdue the ambient light strength. Then you can use slightly lower ISO for better details, flash for color, and following the above advice, better control of the DOF.
Anyway, hope this helps with something to think about. Looking forward hearing from others and maybe seeing their examples.
Oh, yeah, I wouldn't use AI Servo on posed subjects -- for me -- I tend to sway or be moving toward another shot. Joshua is a master of these types of shots with AI Servo and wide open, so I'm not saying it can't be done. Choose whatever method you like for AF point, but I use center/recompose and it works well, or always something positioned in the exact center to focus on.