I find the train and veil etiquette a little interesting (I say if you want a train and veil do it, it’s your day!), but if you really want to stick to etiquette here are the “rules”:
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.
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.