Here's a suggestion: how about designing your facilities with separate air conditioning systems for the dining area and the kitchen? Having only one system tuned to the kitchen temperature is the only explanation I can come up with as to why your dining areas are like meat lockers. ALL. YEAR. ROUND.
Leaving your establishment when it's 65F out there and feeling warm after being in your restaurant is a definite sign that it's TOO DAMN COLD inside.