A little confused as to your question?

Can they get in on their own? Probably not but that would most likely be because an unaccompanied minor would not just be wondering around the airport trying to get into airport lounges.

If you mean can you bring a minor, of course you can. No different than any restaurant with a bar.

I have brought a minor into the DTW SkyClub both when it was self service alcohol and just yesterday now that they serve it to you.