That isn't close to being good enough in the UK and the 21st century.
If the Mosque had organised a Fun Run for Men and Boys, and a separate one for Women and Girls, that would have been ok. Sporting events are one area where women and girls often feel more comfortable having a female-only event.
But there is a growing issue with fundamentalist Islam in the UK, and its requirement for Muslim girls once they reach puberty to cover up, avoid sport/exercise and to remain at home unless for school or chores. So family/community pressure is being applied to keep these girls' lives small, to prevent close friendships with non-muslims, and protect their 'honour' ahead of an arranged marriage within the family.
We should push back on this whenever possible.