I totally agree with the sense of working with the character that you have created, so that you can know it better and then create a deeper story with it. As you suggest, there are plenty of activities that can be done using this character creation activity, but of them may be overweight for children.

So, my proposal would be to try make the activity cross curricular in the sense that the activity with the characters may facilitate the learning of other topics that children have to study using the characters, such as, explain how their characters would live if they were in the Middle Ages.

In conclusion, I would say that these activities of the characters have lots of possibilities and that if it is used properly, children can really enjoy the activities while they are learning.