Hmm .. that journey is surely more than just a weekend trip ?
There are direct flights and trains for this journey. Catching a direct flight is the fastest way to do this journey. Direct trains are available as well. Mumbai (Maharashtra) to Cochin (Kerala) distance is 1544 km and you can get there by flight in just over 1 hour and 50 minutes. Going by train won't be that fast but you will get fares starting from ₹ 515.
Beautiful weather for sightseeing and other outdoor activity.