I have a couple of ideas.
Do you want to go where everyone else goes or do you want to avoid other people? I'm in the avoid other people category but some of my ASMs like the cachet of places like Shasta & Whitney. How tough are you and your Scouts? :-)
My troop did a 40 miler over the Memorial Day Weekend at Henry Coe. It was planned as a tough hike because I need to make sure my troop is in shape for Philmont. Henry Coe would be harder in August than it is on Memorial Day.
The itinerary was Hunting Hollow to Wilson Peak Friday Night. (4.3 miles)
Wilson Peak, Pacheco Falls, and Pacheco Camp to Mississippi Lake (16.2 miles) on Saturday. Pacheco Camp is a nice place to camp if you'd like a more relaxed trip. The side trip to Pacheco Falls (now dry) is a little less than 1,000 feet of elevation in a little less than a mile each way.
Mississippi Lake to Jack Rabbit Lake via the Hartman Trail (steep downhill even by Coe standards), then to the Orestimba Corral on Sunday. (13.4 miles )
Monday was Orestimba Corral to Dowdy Ranch. (6.1 miles)
My guys had a blast. We all slept well and it was great to see how jazzed they were on Tuesday at the troop meeting.
You could easily extend the trip north from Mississippi Lake to get a few more miles.
If you've been to Henry Coe, you know that it's tough terrain. In August, it will be hot and dry, so you'd need to practice good water management.
Last year I did a 100+ miles walking from Lassen Park to Susanville.
That itinerary started at Helen Lake, then to Bumpass Hell and Kings Creek. We picked up the PCT for a while where we forded Kings Creek. Then north to Cindercone, the Fantastic Lava Beds, the Painted Sand Dunes, and the Butte Lake Campground. Climbing Cindercone is a challenge - imagine a 2,000 foot tall pile of beach sand - but you get a great view of the Painted Sand Dunes.
From Butte Lake we hiked through to the Caribou Wilderness to Triangle Lake and the Silver Lake Campground. From there we hiked to Westwood for Pizza, then took the (~30 mile) Biz Johnston Trail to Susanville.
With a rest day at Silver Lake, it took us 8 days IIRC.
I can provide GPS tracks for those trips.
I'm thinking of something for summer of 2010. One possibility is to start at Warner Camp in Mt Lassen Park and head north along the PCT to Burney falls and beyond.
Patrol Leader of the Steam Engine Patrol (Huff, puff, huff, puff)