Not every performance is a standing ovation performance. Not every soloist deserves an encore. Those are for things out of the ordinary. That is why encores and standing ovations exist.
It is not better for your child if he is brought up to expect ridiculously inflated applause for every achievement or mere stage in his life. It is doing no favors to your local ballet or orchestra. Either they know you're lying to them, and are embarrassed, or they don't, which is embarrassing.
Also, one needn't applaud every thirty seconds during a ballet. For virtuosic solos, yes. For big set-pieces, when they end, yes. When Jeffrey Gribler spins for a minute and a half, yes. For every tiddling jeté, entrechat quatre, and pirouette, no, no, no.
One does not applaud when the curtain goes up! You are confused! It is time to applaud when the production is over, so you know how it went.
I know you don't know anything about art, but, seriously, it gets better than this. You could pretend to be blasé.