The two best locations to consider are Lohagad and the Andarbhan Trek as both these hikes are very easy. In the Andharban trek, if you walk for an hour through the forest and return, you will still have a great experience. Children especially love playing in the numerous streams and waterfalls that come along the way. In September, the monsoon rains reduce substantially making these two destinations the top choices for treks near Pune with families.