As some CMs can accept the preschool funding grant for children over 3, I assume that means that the CMs can offer the same 'curriculum'.
However, I would wonder whether there are somethings that a preschool could offer ('school-type' environment, more structure, more children the same age) that would be harder for a CM, and much harder if they are your own child (e.g. taught by someone not your parent!).
Would you be able to claim the grant funding for your own child?
While my DS does learn some stuff at preschool, I feel he mainly learns about managing in a different environment, learning from and with other people and socialising.
There is no requirement for children to go to preschool at all, whether you are CM or not, so if you feel that you are his best teacher and he would be better not to go, just don't send him.
Clearly, he will spend far more time with you than he would in preschool, and you will teach him everything you can anyway, whether or not he goes to preschool (I mean - he won't learn any less form you for being at preschool for a few hours).