The first poster on this thread was basically right. If you're bringing in video, just make sure your movie size is set to whatever your TV resolution will be. The resolution of your Flash movie is only important for the video or rasterized (bitmap) graphics that you use in Flash. Any native graphics and text that you create within flash are totally resolution independent and can basically scale to any size.
No traditional video solution will give you the versatility that Flash video will, but you may not need that versatility for your application, but if you're planning on using Flash, then you probably already know why you want to use it. I'm sure you could pay a videographer to put some titles and effects on your video and export it to an AVI for you, but that still gives you no control over the player interface, looping, or other programatic issues that may be associated with creating your standalone application. It sounds like you're on the right track. Just create everything at your target TV resolution. If this is for standard TV resolution you can use 640x480 and it will look great. If you are doing HDTV it will generally be either 1280x720 (for 720p) or 1920x1080 (or 1080p). Be sure you know the exact output resolution so you can totally avoid scaling your final movie. Scaling during playback will reduce the quality and can drastically degrade playback performance on slower machines (causing stuttering during video playback).
For more info on resolutions, check out
Display resolution - Wikipedia, the free encyclopedia.