There is nothing wrong with the strong leaving Muzdalifah with the weak if they are a single group

No File Exists
Check below answers in case you are looking for other related questions:
He tried to stay overnight in Muzdalifah but was not able to – what is the ruling?
Is it permissible to offer the hadiy of tamattu‘ outside the Haram?

No File Exists
Related Answers:
Conditions and obligatory parts of tawaf
Delaying stoning the Jamaraat during the days of Tashreeq for a necessary reason
He is not sure whether he threw six or seven pebbles when stoning the Jamrah on behalf of someone else
He tried to stay overnight in Muzdalifah but was not able to – what is the ruling?
Is it permissible to offer the hadiy of tamattu‘ outside the Haram?

Recommended answers for you:
Making up prayers at times when prayer is disallowed
Ruling on perfumes containing alcohol
Our attitude towards Yazeed ibn Mu’aawiyah
The virtue of patience
The status of the imams of the Ithna ‘Ashari Shi’ah