I can get permitted for:
1) High Trail - 8.5 miles to Thousand Island and 2,400 foot gain
2) Rush Creek - 7.4 miles to Thousand Island and >3,300 foot gain
High Trail is 7.8 miles from AM, and by your mileage, you must be considering the route south of Agnew Lake, don't do it, very steep, dry, and dusty trail, did I mention steep, not what you really want to start your trip off with. HT is much more scenic and depending on when you are going, the wildflowers (and mosquitoes) will be abundant.