Go with the dominant eye. But I would teach them to be ambidextrous while they are young and before habits are ingrained. It can come in handy for awkward shooting situations and especially if eye dominance changes or an injury occurs. A shotgun I would still go with the dominant eye but let them try both ways.
One thing good about shooting left handed is I am not constantly tempted to get another rifle as there is not a lot of choices out there and I pretty much have all the bases covered sometimes 3X over.
But the key point is that there are choices and many more if you want to spend the $$$ for a custom job. So if one prefers or is required to get a portsider there's no reason not to do so. Remington being out of production seems to have tossed a monkey wrench into the works for both righties and lefties. Wish I'd bought up Midway's stock when they were clearing them out.
