Dillon can be nice. I live in Silverthorne so am keeping an eye on it and paddled it once this year. It is low due to 2011-2012 lame amount of snow. They say it will get within 7 feet of full this year, it is adding water daily but end of June would be best. Put in on the Damn road day use area. Or camp right there in the campground. Have a cart.
I've done Shadow mountain, it is cool, Trappers Lake is the largest natual Lake in Colorado, The Flat Tops, I have never been there, heard is is nice, in a Wildness area so nothing with wheels can be used from the campground, long portage, there is a Lodge they say you can put in.
Grand Lake is a natural lake and because of that, law requires the water level can't fluctuate by more than a foot, it is connected to Shadow Mountain so maybe them to.
Many speed boats on Shadow mountain, Trappers and Willow moters aren't allowed.
I have always wanted to go into the Tetons with one of mine, remote campsites on a few lakes.