幼児と外で遊んでいて毎回思うことです。 - Every time, I’m playing outside with my infant.
ズボンに泥ついてるし – my pants have become muddy
手も真っ黒だね – my hands are so black
お尻に草ついてるし – there are grass stains on my bottom
「いつの間にこんなに汚くなってるの〜」は
How did your pants get so dirty so quickly?
I can't believe your pants got so filthy so soon.
と言えます。
「ズボンに泥がついてるよ。」
You got mud on your pants.
「手も真っ黒だね。」
Your hands are all black too.
「お尻にも草ついてるよ。」
You have grass stuck to your bum as well.
ご参考になれば幸いです!