When my children grow up to be adults, I just want to take care of myself.
But that probably won't happen, since I'll be asked to take care of the grandchildren and so on.
ご質問ありがとうございます。
"When my children grow up to be adults,"=「私の子供たちが大人になったら、」
"I just want to take care of myself."=「単に自分のことを気にしていたい。」
"But that probably won't happen,"=「でもそれは多分、起こらないだろう」
"since I'll be asked to take care of the grandchildren and so on."=「孫の世話などを頼まれるだろうから。」
ご参考になると幸いです。