Hi Jen,
My daughter is just 8 months and we started Cheerios 2 weeks ago. She actually threw up the first time we tried them, but she still wanted to play with them. We kept a very close watch and a few days later she had figured out how to mush and chew them. She does have 2 bottom teeth that really help out- does your son have any teeth yet? Just wondering if this could be the reason? Teeth or not, I think that with trial and error, and as long as he is getting other solids, he'll figure out the chewing part soon. You can always give teething biscuits in the meantime- he can't choke on those (although they can be broken into bits so keep a close watch!)
Good luck!
Andrea : )