I probably wouldn't. There are so many good choices in the resorts that I'd just do that versus add a day to my tickets. I know that the difference in price to add a day is pretty small when you have a lot of days on your pass, but when you multiply it out, it can add up fast.
Just because I wouldn't, doesn't mean that it's not the right thing for you to do though. Just figure out the cost to add the days, and ask yourself "Is eating at ________ worth paying a $______ cover for" or "If they were going to surcharge me $_______ to eat at ________, would I still go?"
If the answer is yes, then go for it!