Of course it's OK, as long as it gets him to eat. I mix quite a few different things together in order to get DD to eat it. She likes some veggies by themselves, but some i have mixed with fruits or other favorites to get her to try them. I myself eat lots of things mixed together, so I don't mind if that's the way she likes to eat. Also, when introducing a new food, pair it with a favorite first and then transition to it by itself.