You can go to Lonavala or Matheran or Mahabaleshwar if you're looking for a hillstation.
If you're looking for camping, there's Pawna lake near Lonavala or Bhandardara. For fun parks, you can go to Imagica or Aquamagica near Khopoli or Della Adventure resorts near Lonavala.
Check out Bhandardara, dist. Ahmednagar. It's an amazingly beautiful place. There's mountains all around. Bhandardara is situated in the midst of Sahyadri range. You must visit this place once at least. Check out The Land Of Wanderlust (TLOW) website..... https://thelandofwanderlust.com/