Hi fschmidt!
I want to commend you on your desire to raise your children in a better environment and to allow them to be open towards other paths of faith.
If you don't mind me asking, how old are they?
I read through the thread, and I don't think you should have a problem finding muslim friends for your kids or raising them in an Islamic environment if those are your intentions. I personally have an atheist friend who I enjoy discussing religion and sharing theories and ideas with, it's really enlightening and she considers me a good friend. I've never felt compelled to become atheist nor have I ever tried to convince her to become a Muslim, but I do enjoy speaking about Islam to her, and she really respects me and my religion and has supported me on many occassions. Now I'm not saying all atheist and Muslim relationships are going to be as similar as ours, however this is not something impossible or difficult either.
To answer your concerns in your first post, Muslims should show respect and kindness to those of any background and faith. Usually a mosque has sermons on Fridays which anyone is free to attend, and through out the week there are prayers and perhaps evening classes and events depending on the mosque itself. The sermons range from various Islamic teachings and topics. The men and women are generally segregated. Both the men and woman should be dressed modestly (women cover their heads and cover their bodies with nonconforming attire according to the islamic dresscode, and men can wear anything as long as it also follows the Islamic dress code). If you go to a local mosque, you may want to ask some of the brothers there a little bit about the classes they provide, maybe activities or events that they have in which you and your family may be interested in participating in.
Concerning the topic of monogamy, Islam does not condemn polygamy however it's not strongly advocated either, but marriage is. We consider marriage to be very important and a beautiful aspect of life and combined with the obligation of chasteness, it allows us to keep our priorities in line and when we feel we are getting close to where we think we are prepared for marriage, we have a better insight on the responsibilities and committments that are expected of us as spouses.
I am reading the Quran now. I just read 3:118 which says:
"O you who have believed, do not take as intimates those other than yourselves, for they will not spare you [any] ruin. They wish you would have hardship. Hatred has already appeared from their mouths, and what their breasts conceal is greater. We have certainly made clear to you the signs, if you will use reason."
So I guess this settles it, an atheist cannot be accept by the Islamic community. Am I understanding this correctly?
Islamically we're not allowed to get too close with a nonMuslim because they may influence us due to a close emotional bond, and in result we may stray away from our religious obligations. So the meaning of that ayah is basically that we shouldn't get too close to those who condemn and reject our religion lest they have intentions to change or harm us. However, we are encouraged to spread Islam and teach others about our religion and create bonds in that respect where we can benefit others positively and at least warm their hearts through our kindness, and love and devotion to our religion.