Batshit to brilliant- how would you rate this parenting technique?

[Thistledew]

DS is just 6. He is suspected of having some ADHD traits. He is a smart kid but has some behavioural issues that we are working on. One example of big flashpoint is getting him to put down his tablet and come and eat dinner when we ask him to. If he is tired, or otherwise overloaded, a request to come and eat can be met with rudeness, refusal to do as asked and tears. We are trying to deal with this by letting him know that the transition is coming up, and consistency of expectations and consequences.

An idea has been mooted that a trusted person (grandparent, who visits weekly) should share a code word with DS and will use this code word when DS is getting overwrought, and it will signal to DS that he needs to calm down and do as he is told straight away. This is to be a secret between DS and the grandparent and not shared with DH and me.

So,

IABU - batshit
IANBU - brilliant

What do you think?

My DS is autistic and has ADHD and I let him bring his tablet and headphones to the table with him. Something are worth the battle, this isn't one of them.

He doesn't sound like he has adhd (and dont even say adhd "traits". Cuz literally everyone alive has adhd "traits". Doesnt mean you have adhd)

sounds trouble with rules Re ipad. Give him better boundaries and less ipad time if it is causing so much stress.

Chill out box. We use timer, ds throws strop still about coming off ipad. We stick chill out box beside him - blanket, fiddle toys, cuddle toy. Then leave room and give him 5 mins

It won't work

To me it seems that this grandparent has a fundamental and complete lack of understanding of your ds's condition. It is undermining your parenting and basically gives the impression that the grandparent thinks that you aren't capable of getting him to do as he is told.