Hello shahid, I see that there’s no bus from Dandeli available for Goa, there are buses from mangalore which will take around 8hours to reach Goa.
So, it’s better if you convince your college faculty to start the visit from Dandeli and end the trip in mangalore.
Buses from Manglore:
https://m.redbus.in/search?fromCityName=Mangalore&toCityName=Goa&fromCityId=95222&toCityId=210&busType=Any&opId=%3CopId%3E&doj=23-Mar-2019 If you are with around 6-8 friends then book a hostel, you may get a whole dorm for yourself on a cheap price.
A scooter would cost you Rs.250-300 a day.