Framlingham Castle is a great day out for the family. It is only an hours drive from Bury St Edmunds. It is great fun for kids, very scenic and perfect for a day away. If you are an English Heritage member, its free!
Historically it is also very interesting as well. Mary Tudor, daughter of Henry VIII and his first wife, Catherine of Aragon, became queen in 1553 after the death of her brother, Edward VI. This was very controversial for a few reasons, her mothers marriage was dissolved on the grounds that she was married to Henry VIII's brother and so he could marry his second wife. This lead to split between Rome and England and formed the Church of England and the monarch became the head of the church. So Mary was Catholic and it was feared that she would return England to Catholicism. Mary went to Framlingham Castle until she was announced as the Queen.
You can walk amongst the ruins and there are some games and activities for children. They also have great events for Easter and Halloween but also some educational events.