I have a Chevy Van with the 9 inch tv /vcr combo sitting inside of a prefabricated wood console. It's really just a box that sits on the floor, with holes cut out so you can pass the cables through for power, antennae, and external speakers.
The tv just sits on the floor, it isn't attached to anything, and it has never fallen out or bumped against the top of the box or anything like that. It's been in the van since it was new, and that was in '93 and over 130,000 miles ago. I have had to remove it a couple of times to make more room for access to the doghouse, so I know there isn't anything holding it down except gravity.
I think the weight of it keeps it situated on the floor and I never drive 'off road', so it just has to contend with the bumps that I try to avoid anyway.
As far as avoiding the sun light for tv viewing, they make sun screens that have little suction cups on them that you can move from one window to another, if you had two of them, you should be able to adjust them and move them as needed.
I'm sure that the heavy duty type velcro would be sufficient to hold it down if you just wanted it to sit on the floor in the middle of the front seats or something like that.
If it has an external speaker jack or a headphone jack, you can get an adapter at Radio Shack to connect two headphones into one jack, just be sure to match the size of the plug correctly.