Yes, I fully agree Ohana wouldn't be up to the task of preparing the meals. However, psychologically thinking the chef might have recuperated really fast if Ohana had appeared in the kitchen to try to cook fancy meals, especially if she had told the man to forget the consultant's bullshit and just do things like he always does (because I've no doubt he never serves second-rate food in the first place). This would have taken ten minutes instead of a long bike ride, train ride, and running through the city, randomly searching a big building - and whatever is going to happen in the next episode. Let's not forget they were already preparing the meals; how long will the customers now have to wait?

However, naturally for the story this development was more interesting. And like I said, it suits Ohana's personality.

Zell, I think the son is just stupidly in love with the woman and his filters are all offline. Thus anything she says will sound like words of a sage in his ears and, moreover, he probably subconsciously tries to think of plans that would be alike to hers. All to the ruination of the inn.