Had chickens once, hated it. If you do get some chickens, be sure to get a tall pen for them it's easier to clean up and get the eggs that way.
Lots of work, you will have to cut their wings otherwise they'll start to fly around and they might end up fly jumping over the fence. Also they eat a lot and make a huge mess, bird poo everywhere (at least it's easy to clean it as long as it's not liquid anymore).
However on the bright side fresh eggs every day (and for some reason I liked em more than the supermarket ones), if you want more chickens you just leave some eggs to hatch and if you don't want more chickens just don't buy a cock, they still lay eggs, but those eggs won't be fertile.
Anyway whatever your decision may be, Happy Birthday!