Thank you all for the responses! Mary & ColinsMum - you're probably both right that it's too early to tell, and maybe not so useful to try to classify traits at this point. I'm concerned about meeting their needs, but it's not really necessary for me to figure everything out now. Thanks for the book recommendation!
Renie1 - thank you for sharing your experience! The boys do have some self-stimulatory behaviors, but the spelling doesn't appear to be one of them. J seems to enjoy if I sit down and hand him letters as he asks for them. He also thinks it's really funny when his brother kicks through and scatters all of his carefully arranged letters. Thanks for the advice!

Thanks again guys!
Julie