To say grumpy in a nice way, you can use terms that focus on the persons temporary state, their energy level or even quiet focus, instead of their personality.
Some ways to say grumpy in a nice way are to say out of sorts, a bit tired, quiet, focused or serious and reserved.
Out of sorts, suggests a mild, temporary dip in comfort or mood without labeling the grumpy person as difficult.
Saying they are a bit tired, blames the fatigue, lack of sleep or even a long day rather than a bad disposition.
Quiet, Reframes silence or lack of enthusiasm as just needing space.
Focused or serious shifts the tone away from annoyance and toward deep concentration.
And reserved describes a person who is keeping to themselves without making it a negative trait.
Some other context specific ways to phrase the person being grumpy include:
If the person hasn't slept or eaten, you can phrase it as "They're a little low on energy right now."
Or "They might just need a quick break."
If they are short or direct, you can phrase it as "They seem a bit preoccupied today."
Or if you're talking about yourself being grump, you can say "I'm a bit off my game today", or even "I'm running on empty today".
Some alternative ways to say grumpy in a nice way to a child include.
Overstimulated, which identifies that the child is overwhelmed by too much noise, light or activity.
Tired out, normalizes the child's mood by attributing it directly to a lack of sleep or a busy day.
A little out of sorts, suggests a fleeting, temporary mood without labeling them as a "cranky kid."
Having big feelings, validates that the child is experiencing intense emotions that they cannot quite voice yet.
Or in a bit of a slump, reframes the grumpiness as a temporary drop in energy or mood.
Some kind ways of describing a grump child to others includes:
They're having a tough moment right now.
They are running low on fuel after a long afternoon.
Or they just need a little quiet time to reset.