Content Administrators role is a system role designed to have almost as much power as admins. If you want users to only be able to edit then you should create a custom role and give that role edit permissions and create child pages permission on each page in your site, then put your users in this role and remove them from content admins role.

This might be a bit of work if you already have a large site hierarchy, but if you do it from the beginning on all your pages then newly created pages will inherit the same permissions from their parent page. You would probably also want to add the custom role to "Roles that Can Create Root Level pages" from Administration > Site Settings > Security > Permissions

Hope that helps,

Joe