WHEN IT'S THE BRIDE'S SECOND MARRIAGE
If you've been married before or have children it's perfectly acceptable to wear white.
If you've been married before or have children you're not supposed to wear a veil or have a train attached to your dress or carry orange blossoms. (Must be a sign of purity or virginity thing).
The second time around, your parents are not obligated to pay for anything.
If you get along with your ex-husband and his family and it's fine with your fiancé, then it's acceptable to invite them to the wedding. (why you'd want to is another story)