CEED

Do, absolutely, go for it. It is much better than going for an MBA (unless the MBA serves a grand plan of yours). With an M.Des in hand, sooner or later you'll find yourself wanted badly by the industry. The Indian manufacturing/services mindset is changing, and we are moving towards more of a 'build a brand' mindset. The things that'd get us there are:
a) Greatly designed products and services
b) Great marketing
A design course would not just give you the skills that the industry needs, but also a way of thinking that unlocks doors.
I personally have not gone for a Master's degree after Bachelors in engineering, but being in touch with designers has made me hold them in high respect.
For entrepreneurs:
Design thinking makes you see opportunities, and that's great for an entrepreneurial mind.
For professionals:
The pay may be low (though that's changing too), but some of the projects you might be on will have a potentially great impact.
That said, it's really hard work being a designer if you're up for it and for a prolonged period of struggle, a world of wonder awaits you.

Hello,
No, you cannot take CEED just after class 12th. The eligibility criteria for CEED exam is:
There is no bar to either the age of the candidate or the number of times a candidate can participate. The minimum academic qualification for appearing in the examination is a Bachelor's degree in Design, Architecture, Fine Arts or Engineering from a recognized college or university of India.
All qualified candidates with a valid CEED examination score become eligible to apply for admission to various design programs under IITs and IISc. A valid CEED score does not, however, promise admission to the desired institute. Candidates are always required to appear for a second test known as the Design Aptitude Test followed by an interview prior to final selection by the respective institutes.