I echo with few of below mentioned suggestions given by different travelers you can also visit Igatpuri as well .I also want to check with you if you are from Mumbai and interested in travelling and joining our travel buddy group from Mumbai currently we are around 25 buddies mix age mix gender in group
You can try Matheran and Karjat farms, although these places are just like Lonavala and Khandala but apart from this you can explore Alibaug, Panchagani, Mahabaleshwar.