Dude!
If Sunday is fine with you, book in 12224 from Ernakulum till Mumbai LTT. That train stops at Madgaon and you can de-board there but since the train is a Duronto so bookings can only be done end-to-end.
Reasons for preferring that over this:
Availability status is 'Available 1' at the moment.
Much...
more... MUCH better train!
Swanky new LHB rakes!
Complimentary food! On-board services!
A better time of reaching Goa!
Covers the super-scenic Mangalore-Goa route in day time!
1A experience in that train will be a memory to last trust me!