I recently moved with my family from 'high density' living in the city to the suburbs and the truth is that the city actually had more outdoors / free activity space for kids, than where I'm currently at. There where at least 3 playground within easy walking distance of our apartment in the city, a school yard with outdoor basketball courts kids could play on after hours, plus a large city park/botanical garden with huge open spaces a 5 minute bus ride/ 20 minute walk away.