Just let us know how we can help, that goes for both of you guys. I can direct you to specific reading materials if that will help. Also I (along with many others) am here to answer questions as best I can; whenever you ping this thread I'll definitely respond.
I think sometimes polyamory isn't something you understand, it's just something you know about and support your husband's interest in it however you can without compromising your own needs and morals. Right now I think the important thing is cooling the engines with M. Maybe a better poly match will come along in the future, who knows and that's not something that has to happen by any means.
Children are a blessing but everything I've heard suggests that nothing can prepare any new parent for life with their first newborn. I think poly will have to go to the back burner for awhile, it'll just be self-evident. You have a strong marriage and you'll get through the challenges together. Just let us know how we can help.
Love means never having to say, "Put down that meat cleaver!"