Hi Scott,
The wake up feature happens automatically to keep things simple, but Citrus won't wake up the computer if there are no alarms scheduled or if the program has been shut down, so the easiest solution for now may be to close Citrus while you're travelling, or disable all your alarms temporarily.
You may also want to configure your system to go back to sleep after a few minutes of inactivity so your battery doesn't get drained for very long if an unwanted alarm does activate.
If your computer is still being woken up even after shutting down Citrus or disabling its alarms, a different program is likely waking up your system, such as a Windows scheduled system update or virus scanning software. (Note, for example, it is not possible for Citrus to wake up your computer more than once after it has been uninstalled entirely, since scheduled system wake-up times are for very specific moments, and cannot be repeated automatically without something like Citrus running to re-schedule it after every time. Citrus also clears the scheduled wake-up time when it's quit, so waking up even once while it's not running is unlikely, unless the program was force-quit or if the computer lost power.)