Went there a few years ago with young kids on our own. It didn't even occur to us to take a tour. Even if you're not outdoorsy, just follow the signs, park in the parking lot, and walk along the well marked paths.
And the paths aren't that difficult. I don't know if your children have any special limitations, but the average 7 year old would have no problem doing a 1.5 mile hike. That should only be about a 30-40 minute walk, so even if they are a bit slower, you'd just arrive at the end a few minutes later than the group. (A typical rule of thumb is that kids should be able to hike 1/2 to 1 mile per year of age, so the average 7 year hold would hike about 4-7 miles. Our 4-year old did a 6 mile hike. And then there are the extremes, like the 4 year old who hiked the Appalachian trail, averaging 13.5 miles a day for 2,193 miles:
https://www.advnture.com/news/how-a-4-year-old-hiked-the-length-of-the-appalachian-trail)