While it's understandable for their children to sit down, their physically unimpaired parents should give their seats to people with disabilities.
こんにちは！
ご質問ありがとうございます。
ご質問について、いくつか言い方が考えられますが、例えば、
On a weekend evening, exhausted parents and their children sit on the priority seats on the train. While it's understandable for their children to sit down, their physically unimpaired parents should give their seats to people with disabilities.
とすると、『ある日の夕方、優先席には、遊び疲れてぐったりした親子が占領して座っています。子供が座るのはよいとして、健常な親は[障害者](https://eikaiwa.dmm.com/uknow/questions/4085/)に席を譲るべきです。』となります。
参考になれば幸いです。
日本 
