Things to be noted!
Its difficult to find pure veg restaurant in South so here are some places which one can try.
Munnar- Annapurna pure veg
Thekkady- Hotel vasant vihar
Ooty- Kailash parvat for North Indian cuisine
Anand bhavan for South Indian cuisine
Southern India is all about its natural beauty so prefer personal vehicle over public transport for convenience to explore beautiful places on the way
Language issue is going to be there especially in Kerala region.
Distance between two places may be less but it takes more time to travel because of hilly curves, clouds and mists so prefer not to travel after 6 in evening.
Overall trip cost--(Group of 6)
Car hiring for 8 days- 33000
Food- Around 12000 for group
Accomodation- Room between 1500 to 5000
Activities- as paragliding ( 3500 per person) , zip lining, rappelling, house boat stay( 4000-10000 per room), camping (3000 per night per person) which may cost accordingly.