I think I've read this one before. It's a common tale, and while the dialogue is good, I think you can make it better. Give them something more than roam the world, living a 'meaningful' life. Don't make them too cliche.
You might consider making this shorter. Some of the opening dialogue can be culled, and the scene where they steal the firearm can probably be cut. Just give him the weapon already. Yep, he stole if from his dad. This is what he's been planning all along. And you might toss in some real life problems. No passport, no money, no friends or relatives to meet them. Adventure is nice, but make it believable. And they can settle. If they can't fly overseas, they'll drive to Canada or Mexico or someplace.
The final shootout works, although most of the time a shotgun is loaded with shot, not slugs. Same damage but difference ordnance.