Ok, to counter Mono.
Cause I can and he won't mind.
I'm a poly woman, married with a live-in boyfriend and 4 kids.
My take on your situation is....
well the same as Mono's.
I can't help but wonder if she isn't a cowgirl and I find it concerning that they would be discussing children only 2 months into the relationship. Maybe it's just discussing as a future poss. But in terms of parenting, responsibility etc, 2 months is just not long enough to really plan the addition of a child.
I realize that doesn't much address your feelings. I apologize. I never got that far in my mind. My mind did a reeling, screeching, full-brakes slam as soon as I read 2 months.
In terms of poly and children, it can be done and it can be done well. But, just as with monogamy and divorce, it can be done terribly badly too.
(there is also a thread on here about children and poly that you might find helpful)