Indeed, the only way to reduce splatter is to minimize the amount of urine splash coming from your willy. Since it's not practical to ask guys to sit down, let's add some practicality to this idea and introduce a compromise: pee straight down. Anyone who has ever dove off the high board into a swimming pool knows that the way to enter the water smoothly, with a minimum of splash, is to go in straight. The same principle works for your piss. Peeing straight down means that you have to stand so that your johnson is directly over the bowl of the toilet, so that your stream hits the surface of the toilet's "lake" traveling straight down, perhaps a good three inches away from the "shoreline". This will give you some room for error when the stream's pressure drops. (Note: And by all means, please wipe any stray drops of pee off the rim of the toilet--there won't be that many if you master this technique. And, teach your sons to do the same.)

Note that this same technique works with urinals. In some cases this is perhaps even more effective with urinals, depending on the surface area of the bowl's water, and whether there's some sort of deodorizer device sitting in there, because the stream travels less distance and reduces the margin of error. An idea related to this is the following: In some European countries, they paint images of flies in the bottom of some public urinals. The idea here is that it gives guys a "target" to shoot at and it improves their aim. (And, to emphasize a point, you should always aim straight down.)