YOU SAID:
Incorrect is jack goes to picknic
INTO JAPANESE
ジャックがピクニックに行くのは間違っています
BACK INTO ENGLISH
It's wrong for Jack to go on a picnic
INTO JAPANESE
ジャックがピクニックに行くのは間違っている
BACK INTO ENGLISH
It's wrong for Jack to go on a picnic
That didn't even make that much sense in English.