As you have not mentioned if you will be travelling in your own car or by local bus or by train, I am unable to provide further details. Roads in Karnataka are very bad specially between Manglore - Madikeri - Mysore.
go to kabini only if you are interested in wildlife and get a feel of rural karnataka bordering the forest. Coorg is much greener,lower temperatures and better options for siteseing and leisure.
can we go to coorg and Kabini frm manglore n back.. will the drive too tedious? is the jungle resort open in july in the rains? is it worth going in July? cheers KISH