I strongly recommend against introducing cereals, now or ever.
When our daughter reached 6 months, we were relatively new to paleo, and were not confident enough to follow paleo for her. Therefore, we introduced cereals. The result was that she is still, at 5.6 years old, highly addicted to baked goods; we have not been able to convert her to paleo. And, ever since she started preschool - including now in kindergarten - she gets a new cold every week or so for nine months of the year, which seems to be pretty much par for the course for nonpaleo families. She's currently on antibiotics for strep throat, the second or third time that has happened.
By the time our son came along, we were more confident, and we never introduced cereals - his first "solids" were fruit purees, along with pork spare ribs. At 3.9 years old, he's been in preschool for a while now, and he hardly ever gets a cold. He has never needed antibiotics. He does eat small amounts of rice because he sees his sister having it, but it's limited to a couple spoonfuls a week, which doesn't seem to have hurt him yet.
I don't know if you are currently breast feeding your 9 month old, but if you are, I recommend continuing to do that, rather than switching to cow's milk. If you are not, you might do a search and see if you can find the posts from the person who used a raw milk mixture for his child.