Right now there's no way to specify what children representation is, except specifying ElementChildrenAttribute inside JSX namespace. It's heavily coupled with React representation for children which implies that children is a part of props. This makes impossible to enable type checking for children with implementations which store children separately, for instance https://github.com/dfilatov/vidom/wiki/Component-properties.
Probably it could be ElementChildrenProperty (like ElementAttributesProperty).