The only tool you have is the xs:string pattern restriction as in below. CDATA is just an alternative to escaping with entity references. You should use entity references in your pattern.
<simpleType name="NewType2">
<restriction base="string">
<minLength value="5"></minLength>
<maxLength value="30"></maxLength>
<pattern value="(<html>).*(</html>)"></pattern>
</restriction>
</simpleType>