I'm 71 too and don't consider myself to be elderly, but I've met people ten or more years younger who think they're old.  It depends on the person.  I don't have parents living, but could have in theory, so would think they were elderly.  I remember being 11 and thinking the school head girl was incredibly old - she was 19!

Ambulances should be called for anyone who appears to need one regardless of age.  If you've called one unnecessarily, that's better than not calling one and finding out later you should have.