The slaves often had take care of the camels while on the hajj. There were around 1000 camels that needed to be taken care of and 100 of them had gold tied to them.
There were a total of 60,000 people that were on the hajj and there were 12,000 slaves that were mansa Musa's personal assistants. Mansa Musa's had 500 slaves carry his gold until they arrived at Mecca.
People of all ages went on the hajj because it was felt that it was the most important part in being muslim.