Have you figured out the voltage and power requirements of all your bits and pieces?
I second this. GPSs are power hogs.
The mintyboost boosts voltage by drawing more current. While the batteries you have in mind, along with the mintyboost, will provide the voltage that you need, and possibly even the current that you need, how long will they be able to do that.
Expecting 3 AA batteries to power your device for more than an hour or so is unrealistic.