We do support CAA records, but we would need to add them for you in the back end system. Please login to your iwantmyname account and send us a request via our support form to provide the required security authentication.
Also include the syntax needed for your CAA record: <flags> <tag> <value>
E.g. 128 issue "mydomain.com"
Once we have that information we can make the update for you. In the mean, time if you have any questions, just let us know.