Given that you are going in mid-June, with 11-13 year olds, and looking for a lighter adventure, you mightconsider just backpacking and camping along the Pine within the Weminuche boundary. The gradient is very light in this area and, hence, should make for an easier hike.
The Pine in the Weminuche is great for fly fishing. Plus, in the slower parts of the river, you could run a kayak with no serious concerns. If you are looking to climb a high peak, though, you'd have to hike a bit.
Of course, this section of the trail gets used a bit more than others. But for those not as serious in your group, like the parents, this might be a plus, as they wouldn't be entirely alone out in the wilderness.
If you aren't familar with this section of the Weminuche, let me know and I'll post some more info or you can just email me.
I hope this helps! It will be a fun adventure wherever you go!