First pick: stranger
Last pick: co-worker
Everyone in between: don’t care.
If the family members include someone who has seen me naked before, I pick them. Otherwise I go with a stranger.
(No friend has ever seen me naked. For one thing, most of my friends are women and married.)
I piked stranger because you don’t have an all of the above - I effectively have no body modesty after being suck in hospital so damned much I just don’t give a shit any longer. You don’t like my fat 53 year old arthritis ridden body, deal with it.
Don’t get me wrong - I take pains to shower frequently, keep my hair and clothing clean and neat, because there is nothing good about a fat sloppy dirty broad with stringy greasy hair and ratty clothing. [or even a skinny broad with nasty ratty hair and clothing] but appear naked in front of some random person because I was forced to? Meh.
Don’t care, not shy.
But picked “Friend” because most of those have seen me naked plenty, whereas none of the other categories have (by the OP’s examples, I took “Family” to exclude my wife and kids, who see me naked all the time anyway. We’re not very prudish, chez Dibble.)
I pick stranger not exactly out of my own modesty, but to protect the modesty of my relatives and friends. I bet my sister in law doesn’t want to see me naked, so she’s out. Strangers, while they maybe don’t want to see anyone naked, I don’t know them, so tough luck.
Most of my same-gender friends have seen me naked or close to on multiple occasions. I’m not a prude, and when we spend more than a few days together with activities that require clothing changes, we shrug, strip, and redress.
As a high school freshman, all of us (males anyway) who wanted to play sports that year were required to strip down and get a hernia exam (‘turn your head and cough’.) All of us in one big room. There were friends, strangers and even family members in some cases. So I guess all of us would have answered that we’d get naked of anyone who asks.
I’d resist the tin-pot dictator for fun then give in and strip. If I must pick, I’d let a stranger to see me naked. People I like shouldn’t have to see this.
Could be any of the options – why would I care?
I picked “stranger” because that would be the most convenient - just ask one of the guys next to me in the locker room of the gym.
Regards,
Shodan
Another “don’t care.” Now if I here particularly hot and attractive to anyone then it may be different, but really the choice is who should suffer?
I’m sure that all of my relatives / friends / acquaintances have seen naked, middle-aged bodies before.
So does this mean we know which relative, which friend, etc. we’d be naked in front of?
Not that it makes that big a difference. I’ve skinnydipped with wife, girlfriends, friends, acquaintances, and strangers. It’s not that big a deal to be seen naked.
“Stranger”. I would never inflict my hideousness to someone whom I cared about. 
For the literal question in the OP: I don’t care.
For what I think the OP really wants to know:
I’ve done the clothing optional festival thing, so I’ve been naked in front of friends and (of course) my husband and kids and strangers, and it was no big thing. Although these days I mostly do so out of convenience - getting something from the car or running to the john - rather than as my outfit for the day.
The year my dad came was the first year I stayed clothed. No idea why, it just felt intensely awkward and uncomfortable to be naked around him. My discomfort was both for me and for him. He’s now been to the same festivals for several years running, and the discomfort remains. Before he arrives, or if he’s on a town run, I don’t have any inhibitions about moving around unclothed as convenience dictates. But when I know he’s on the grounds, I at least throw a cloak on.
Like most everyone else - not an issue.
But as long as we get to choose, I choose Flyer, since you’re so curious!
Frankly, you forgot the option “whoever, I don’t care, no big deal”. It won’t taint my relations ifthey’ve seen me naked.
Frankly, you forgot the answer :" I don’t care. Whoever". I’m not accustomed to being naked around people, but it wouldn’t be a big deal for me if I had to.
I’d choose someone I didn’t like cause it is gonna put their eyes out.
I pose nude for artists, hang out with burlesque performers and community theater people, and work for a publisher of erotic romances. I have very little modesty left, and any of the above people would be perfectly able to look me in the eye afterwards. The only reason I’d pick “not my family” is because I’d sincerely like to never be in a room with any of my relatives ever again.
You didn’t include an “All of the above” option. I’d make them all suffer.
If I am being forced, who cares, it just means I was not being as aware as I should have been