A letter from the Archdiocese does stipulate however that if you do eat meat on that Friday you must then "undertake a work of charity, an exercise of piety, or an act of comparable penance on some other occasion during the Second Week of Lent."
Normally having to eat or even just smell boiled cabbage might be penance enough for some people. Even so, I would encourage you on another day not just to do a comparable penance but an even more substantial one to show your appreciation for the gift of the St. Patrick's Day dispensation we are being given.
There is a true story about astronaut John Young smuggling a corned-beef sandwich aboard the Gemini 3 mission to space in 1965. NASA engineers had required that all of the food to be consumed by the astronauts in space be compressed or puréed and put into tubes. This was done because there was a danger in the weightlessness of space that food crumbs could float into the spacecraft electronics and instruments and cause problems.
Astronaut Young ignored the food directive and tucked away a corned-beef sandwich in the pocket of his spacesuit (the photo shows the remains of the sandwich which are still in a museum in Indiana). At some point in the mission Young pulled the sandwich out, took one bite, noticed some drifting crumbs, and remarked, "It’s breaking up. I am going to stick it in my pocket."
Such tiny crumbs yet they could have wreaked great havoc. That is one of the most central lessons of the season of Lent. Pay attention to the little things. Often it can be one little movement of attitude, one brief remark, or even a subtle expression on our face that can make a big difference.
One dispensation from the Archbishop might cause some people to grow lax in their Lenten observance. It could even cause them to shrug off even greater duties of the faith. Or, it could cause us to reflect on the true aim of Lent. It could inspire us to surpass a mere rote observance of the Church's precepts and to offer more meaningful gestures in a more authentic spirit of love.
Don’t let your Lent start breaking up. Do the little things well and big blessings will follow.