Is their marriage considered valid, what are the consequences of the previous relationship, and must the husband be informed about it?

You have done well by repenting, and Allah accepts repentance from His servants, so have a good opinion of your Lord. Live with your husband as if nothing had happened, and be diligent in raising your son upon goodness. Real zina (fornication/adultery) is that which involves penetration into the private parts, and which necessitates the prescribed punishment (hadd), and which prevents marriage. Since penetration did not occur, you are not a zaniyah (fornicatress/adulteress), and your marriage is valid. You must conceal what happened to yourself and not inform your husband; for concealment is required and obligatory, and you will be rewarded for adhering to it. The loss of virginity has many causes other than sexual intercourse.