There are many ways we can understand this question.
Firstly from the legal aspect, as of 20 April 2020, we are still allowed to participate in recreational activities in parks like walking and running. But remember to wear a mask (unless your kid is 2 years old, then it's not needed as of now). But be mindful, the government can change this law at the drop of a hat.
Secondly medically speaking, the risk is low as long as you maintain the social distancing rules and you maintain good hand hygiene while outside. Once you return home, immediately go and bathe.
Lastly, there are advantages in exercising outside for mental health, sunlight is good.
But you have to balance that with the possible risk of catching the COVID-19. The only way to have zero risks of catching is for the entire household to completely hide at home and not order anything or go outside at all.
If you cannot go out, you still can exercise and have fun inside the house with the children. Take care and stay safe!