Alternate feet
If it's too easy, try left, then right, then left again, so no favourite foot carries the whole ladder.
Solo keepy-uppies get boring fast for a beginner, mostly because it's just them failing alone.
Judged against nothing but your own last attempt, that's especially discouraging when one player is older or more capable than the other. Add a partner and a simple ladder and it turns into a shared game instead: one touch and pass, two touches and pass back, three, four, climbing together. Below: why the shared framing takes the sting out of a drop, how to make it harder or easier without changing the game, and scripts for keeping the mood forward-looking.

No equipment beyond the ball
Get in position. Stand a short distance apart, close enough to pass comfortably.
First touch. One of you does one touch and passes to the other.
Second touch. The other does two touches and passes back.
Keep climbing. Three, then four, and on, one more each time.
A drop is fine. Just start the ladder again from one.
One ladder, not two turns
Because you're both trying to keep the same ladder going, a drop isn't "your fault," it's just the ladder resetting, which takes a lot of the sting out of it. It also means an older, more capable player and a younger, less confident one can play properly together, since the challenge is shared rather than split into "your turn against my turn."
A scored version, first to five, or whoever drops loses a point, works fine when both players are roughly matched. It works less well when one of you is six and the other is nine, because the older player either has to hold back to keep it fair, or the younger one spends the whole game losing. The ladder sidesteps that: there's one number, it's either climbing or it's resetting, and both of you are equally responsible for keeping it going.

The evidence behind sharing the goal
A study on children sharing more after playing cooperatively found that children who played a game with a shared, cooperative goal went on to share significantly more with a third party afterwards than children who played the same kind of game framed as a competition.
This is a controlled lab study using a marble-run game with same-age 4-5 year old pairs and a sticker-sharing measure, not football and not a mixed-age sibling or parent-child pair in a real garden, so it supports only the general principle that shared-goal framing is a reasonable, evidence-adjacent choice, not a specific claim about what a keepy-uppy ladder does to behaviour afterwards.
See how Our Kickabout researches its pages.
Harder and easier, same ladder
If it's too easy, try left, then right, then left again, so no favourite foot carries the whole ladder.
A stray touch off the arm doesn't save it, it just becomes part of the count.
If it's too hard, allow one bounce between touches, or if four keeps ending in a drop, let the count restart from three instead of back to one.
Scripts for the actual moment
After a drop: "Good ladder, let's beat it!" keeps the tone forward-looking rather than dwelling on the miss (it's what the game above says too, so the words are ready before you even need them outside).
While you're climbing: counting out loud together, "one, two, three," adds a shared rhythm too, turning the climb into something you're both doing, not something one of you is keeping score of.
Try it on screen
Want to get the rhythm before you're both outside? Play Keepy Ladder here first. Same idea as the real thing: time your tap as the ball drops to your foot, keep the shared ladder climbing, and watch Dad take his own turn automatically. The real version with an actual partner is better, but this is a good way to feel the timing.
Keep going
Not every five minutes needs two people, here's where the rest of the collection comes in.
Three item target shooting is a solo aiming challenge against fixed targets, good when a child wants something to hit rather than someone to play with.
Read three item target shootingSilent dribbling challenge is about controlling the ball quietly on your own, good for a calmer, lower-energy few minutes.
Read the silent dribbling challengeEvery short game and plan on the site, sorted by mood in one place.
Visit 5-Minute GamesTonight's five minutes
Stand a short distance apart, start with one touch each, and see how high you get before tea's ready. A drop just means starting again from one.