Unless down the path is in plain view 3 ft away, good luck with that. Playing with the children is fine, leading them to a vague location without permission will look REALLY shady REALLY fast. You may have to explain to the nice officer why you were bringing the little girl behind the bush… out of the playground…
ETA: I see Scylla had a similar argument (okay pretty much the exact same wording) in mind.
On the flipside
What if she asks to be pushed? I know she may or may not have the “molestation” senses, but by 8 she has a relatively good feeling of what her body feels like. And most 8 years olds are quite quick to say “too fast! I just ate!” And besides, I can say from experience, both knowing myself when I was that age, parental anecdotes, and just watching. Kids are resilient. I mean DAMN resilient. They’re liable to overreact and cry at FIRST but it takes the smallest ounce of positive reinforcement to make them bounce back from just about anything short of being impaled on a spike. When i was little and I fell I cried, my parents told me to apologize to the ground and I was fine, three seconds later. Throwing up is a bit worse, but it’ll hardly ruin her day completely. At worst she’ll need a change of clothes, and that’ll be a hassle of course. But if you talk right she’ll be fine and dandy by the time that change happens. Assuming she’s a typical 8 year old (you know, aside from being the most beautiful creation ever cutting beam of everlasting light through the darkness that is the world, or whatever).
Also, teaching kids to play a game or adding structure to building castles doesn’t ruin their fun. If they don’t like it, they’ll return to what they were doing or generally “Calvin Ball” the official rules until they’re having fun. Not to mention not only are 8 year olds the most resilient beings on the planet, they also get the honor of being the most frank. They’ll pretty much tell someone, adult or no, if something is boring or unfun (remember how quick your daughter was to point out fly fishing was nof un anymore without a hook and fly?). And that’s not just “rude children” because it’s not being rude, they’re just very quick to point out if it makes them bored. And sometimes the structure the adult offers by jumping in allows them to have more fun with their castle. With the more refined and precise motions of the adult they can add more intricate ornaments to the fun and if they don’t, they tear it down and try again, or tell the adult how to do it better. Any adult who is marginally good with kids will pretty much bend to their will… and let them think they are AWESOME at hide and seek of course.
Granted I don’t entirely blame you for at least confronting the random 40 year old inexplicably playing in the sand box with a friendly “oh, hey”… I’d be a tad creeped out too assuming he’s not already playing with his own relative.