Hey, if you're insane, you've come to the right place! Welcome to the club.
There's basically two issues: training for both and racing so close together.
On the racing front, I think the issue will be recovery. If you race the half marathon hard (for you - whatever that means), a week isn't a lot of recovery time before racing again. You need to be more or less fully trained for the triathlon so that you can basically taper a week before the half marathon and then stay tapered for the week before the triathlon, just doing some minimal maintenance workouts to keep you fresh that week. Probably not a lot of running between those two races, though. Personally, I think a week apart would be better than 2 weeks apart, which messes up both training plans.
So, on the training front... I think you're on to something. Take the tri training plan and ramp up the running - you're running 4 times as far as a sprint triathlon's 5k. I'd increase on the long run (up to 10 miles sounds good) and one of the mid-week runs (probably intervals, do extra!).
On the sprint training plan front, online check out Beginner Triathlete, and possibly SlowTwitch. I've also seen training plans in some of the Danskin and other sprint triathlon materials, and in books. There's not a HUGE amount of variety except in where you start - some of the training plans are for flat out beginners - and how much time you commit - some training plans suggest multiple workouts per day, even if they are short.
Sounds to me like you've got it figured out, just need to stick with the plan. For me, the hard part would be not racing the half-marathon at full capacity and feeling tired going into the sprint.
Good luck!