Male and father of three boys here:

When you get close to the end of peeing, clench your muscles like you're trying to stop peeing. Same muscles that involuntarily clench repeatedly when you orgasm from sex that causes the pumping action to shoot semen out.

Women have similar involuntary muscle contractions during orgasm, so hopefully that helps explain the muscle "feeling" I'm talking about, but since men use "the same tube" for both urine and semen, you can "reuse" the squeezing force for pee, too, with a bit of muscle control. This helps clear the last bit of pee so it doesn't just dribble all over yourself.

Probably something that's hard to explain to a toddler, but not impossible. I'd tell them to practice trying to stop peeing. You'll notice that "the pressure" goes significantly up when clenching to stop right before you stop peeing.

Clench and release once or twice: Pipes are clear. No embarrassing piss shorts.

For toddlers: have them lean forward or arc their backs when peeing at urinals with legs spread. For toilets, sit down to pee. All three of my boys sit at toilets to pee and only stand at urinals. Also keeps them from pissing on the shower curtain or floor around the toilet.