How can you express a "double causative"?

Question

Made-up example to illustrate what I mean by "double causative", since that may be an abuse of terminology:

Suppose your grandmother always forces your kids to eat okra, which they hate. You think this is unreasonable and the kids should be allowed to eat what they want. As the grandmother is about to come over, you say to your spouse, "Don't let grandma make the kids eat okra!"

My guess would be something like this:

おばあさんに、子供たちにオクラを食べさせることをさせないで！

Is my attempt correct? What is the most natural way to express this meaning?

Answer 1

No, it is not correct, sorry to say. You literally created a "double causative" in:

「[食]{た}べさせることをさせないで」

But we would not use this structure in a natural setting. It sounds quite wordy and awkward.

Most naturally, we would say something like:

「おばあさんに、子どもたちにオクラを食べさせないようにしてね（ or しようね）。」

For more clarity, one could insert 「[無理]{むり}に」= "forcibly" and say:

「おばあさんに、子どもたちに無理にオクラを食べさせないようにしてね（ or しようね）。」

Needless to say, 「してね」 is a friendly request and 「しようね」 is volitional.

Answer 2

I'd go for the slightly different construction below:

おばあさんに、子供たちにオクラを食べさせないようにしてください。

Make sure that grandma does not make the children eat Okra.