There are a lot of nice backpacking trails in Colorado. So much that I've never been to Philmont. Philmont isn't about beauty, so I understand why scouts would like it.
To answer your question, no, I haven't taken scouts to the San Juans. So you can get better specific trail information from others. However, in other HA trips I've taken scouts in Colorado and Wyoming, the things I'd be aware of is that
1) June in the high country is not summer, it's late winter/early spring and I've had 10 foot snow drifts to deal with over July 4th. Given the run off, trails can be very wet and mudd