From the parents point of view, it would be conveniant to be bring them up as vegetarians also with the awareness of meat, until they get to a age where they would like to decide for themselves with regards to this
Alternatively, bringing them up a vegetarians may make they reluctant to eat meat.
Personaly, I have seen a friend whose famiy brought him up in the first context (above) and then he decided at around 12 years old what he wanted to do. He liked both meat and vegetarian meals, but respected his parents opinions and would mostly eat appropriate meals with them and then when out with his mates or other family members would eat meat meals.
Hope this helps?