Okay. Yeah it would not work if you have mixed shortcode and string content.
Strangely I think your current code should work.. the_content filter should change any shortcode into it’s output.. are you 100% sure you declare your shortcode correctly in the field?
Another solution would be to have two fields. One where you can put in any string and another which would contain only the shortcode.
That way my first example should work.
