There's no harm in watching Twilight. "New Moon" is also easy to understand, but in the end it may be difficult for a child of 12 years old to understand. Eclipses are best watched by adults, because 12-year-old children are hard to understand. There is a passage in Dawn that describes Edward and Bella going on their honeymoon after they get married. Of course there are intimate plots. 12 years old children should not watch. It is recommended that adults tell their children the general content after reading it.
Educational opportunities:
1. In Twilight, Alice insisted that Edward take Bella home to see Charlie, but taught the children that they should tell their parents before going anywhere.
2. In Dawn, Renee Smee shows Bella her ideas or Bella shows Edward her ideas, which can teach children how to share with others.
3. In Dawn, Bella risked her life to give birth to Renee Sime, which can teach children how great maternal love is.
4. James in Twilight, Laurent in New Moon, Victoria in Eclipse and the Volturi family in Dawn can all teach children that evil is invincible.
5. In Dawn, Arnold of the Volturi family finally realized his mistake and repented to the Cullen family, which can be regarded as a good thing to recognize and correct it with children.
6. The 6.Tanya family's support and trust in Dawn can teach children and friends to try their best to help, not to escape, when they encounter difficulties.
There will be more. You can weigh the pros and cons yourself.