“Off MY Derech” (but still “On THE Derech”) – When children turn out more observant - or less observant - than their parents had hoped

What are the major areas of tension between parents and children regarding religious observance?
How should the issues be handled by both parent and child?
Are there differences between baalei tshuvah, modern orthodox and yeshivish in this regard?
Does Kibud Av Ve’eim mean that the child needs to fulfill the desires of the parents, even when the child disagrees?
Must children eat by parents when the children have stricter standards of Kashrus?
Can parents eat by children who have laxer standards?