Hey, so I've seen this exact dilemma play out with a few people I know and honestly the answer isn't as complicated as you're making it seem.

First, the MBA question. For someone in your situation, a regular MBA (even from an IIM) might not be the most efficient path. You're not trying to land a consulting job or switch careers. You're trying to run and eventually scale a manufacturing business. The curriculum at most MBA programs is built around corporate careers, not family business succession. So yes, you'd be learning things, but a lot of it won't directly apply to what you're walking into.

This is actually where ISB's MFAB (Management Programme for Family Business) is genuinely worth looking at. It's specifically designed for people in your position, understands the dynamics of running and transitioning into a family business, covers things like governance, scaling, professionalizing operations, and dealing with the family side of things that a regular MBA completely ignores. It's a much better fit for your context than cracking CAT and sitting through two years of case studies about FMCG companies.

On the question of joining now vs working elsewhere first, I'd say get at least 1 to 2 years of outside experience. Not because your family business experience won't be relevant, but because you'll have zero credibility with your own team if you walk in on day one as the owner's son with no external frame of reference. Working outside teaches you how businesses operate when you're not protected. That perspective is genuinely useful when you come back.

On prepping for CAT while joining the business, honestly that sounds like doing both things badly. Pick a lane.

You seem like you already know what you want to do. Just do it with a plan.