About reading in an accent: I wouldn't worry about that. Children generally pick up the accent of the place they grow up in, not their parents. It is highly likely that he has already figured out the code-switching necessary to correlate a word spoken in his native English speaker accent with your English second language accent.
I would suggest, actually, that you read to him in your first language, as you will feel more comfortable, he will be exposed to a greater breadth and depth of vocabulary in that language than if you limit yourself to using English with him, and it will help his metalinguistic skills (abstract concepts of language), which has long-term implications for reading comprehension, writing, and problem solving in both languages. Even if you haven't been using your first language with him up until now, at 3 he will pick it up in a matter of weeks or months. Also most languages are better for math than English is. E.g., both Chinese (and many other Asian languages) and Finnish explicitly use the decimal system in the names of numbers. Compare that with English, which has the unique number names of "eleven, twelve, (thirteen,) and twenty", that don't sound much like what they are (ten-one, ten-two, ten-three, two-tens).
