Re: scouts...
we have "daisy" scouts, where the kids have to just 'be in K'. And dd4 is in K, so...
The way I approached is to just say she was in K, you could say your daughter has completed K. No convincing needed over here, I did not state her age, although they did ask her date of birth. Now...if you just don't mention her age in particular, they might not mention it. There was a point when we walked into the first meeting where one of the other girls outright asked 'how old is she?' and instead of answering, I just said 'oh she's in K', and asked the den mom, 'that's all right, right?' and she said 'Yes'. By the end of the first meeting the den mom said 'she fit right in!' with (possibly) some significance, as though she'd had her doubts. I was also pleased to see it was a group of scouts up through 4th grade, approx, so she really did fit right in!
(apparently she just barely looks the part of a k'er so I am not sure how your's will 'look' to others)
Their first activity was finding a country to talk about/draw a flag for, learn a couple of scout songs and then they made a yarn ornament. Not a stretch for her other than the manual skills needed for the ornament.