Hey best time to visit these places will be July to September as there Will be lots of greenery.
one things that highlights all the places is their forts.
people usually go to these places for trekking.
Monsoon is the best time to visit harishchandra gad and kalsubai mt. late june to October is best time to travel. u can enjoy waterfalls , greenery , dense fog and clouds at kalsubai and harishchandragad. kokankada is must visit place at harishchandragad fort. both trek is easy to moderate for hike.
July to feb is best. Monsoon are best for trekking and during winter the weather condition will be pleasant and clear sky. If you wish to visit now then do early morning trek to kalsubai first then come back and do overnight camping at bhandardara. Next day start early to harishchandra gad or do night trek (Only if you're hardcore trekker and know the path) with local guide. Enjoy sunrise from harishchandra gad.