Although it is too late for this, next time ask for pre-visit sedation. It is usually a medicine that calms them before they go to the dentist.
My son had a lot of problems with his baby teeth, also... and I was not very good about brushing or flossing when he was young, either. Our dentist was really good, though... he had the root canals done when he was just a few years old, but it wasn't near as traumatic..... it was done with our regular dentist, in a regular chair... they used nitrous oxide to calm him, and he just sat there and listened to a cassette player. He even dozed off in the dentist chair! We didn't use any pre-visit sedation, although I know some people request that.
One thing to watch out for would be the sticky treats.... people think of raisins as a healthy snack, but the stickiness keeps that sugar on the teeth far longer. I think cheese is supposed to be a good snack, because it raises the acidity in the mouth, making it harder for the bacteria that cause cavities to thrive. (I'm just going from memory on this one...)