A little clearer…you essentially want video to run in each thumbnail, but not tied to a timeline. Have I got that right?
You don’t want to use buttons then, because they will always be selectable in a software DVD player. They are also selectable in a set top DVD player simply by entering a button number in the numeric keypad.
Instead, you should composite your video in either PPro or After Effects, then make it your menu background…then your video thumbnails won’t be buttons. You can also do this with Encore (if you don’t mind compressing more than once) by creating an extra project, save it, create your motion menu with thumbnail animation, render it from the File menu, then close the extra project, open the original project, then import the video clip in the extra project folder\Sources\Menus. Set that as the background for your menu, and it’ll do it for you.