If he will stand for it, I would try sitting down beside him and tapping on myself as though I were him, give some reversal statements. You might want to start out with a little humour such as ``Even though this old lady that calls herself Grannie Annie is bugging me again, I'm a good kid. Èven though...

Dear Grannie Annie, I think it is great that you are trying to help your grandson. After all he has been through in his nine years of life, I think it makes perfect sense to surrogate tap for him. While he has seen some benefits to the initial tapping you did with him, he obviously does not see its value...