i say attempt the cake from scratch if youre ambitious enough to! if not, i highly recommend Duncan Hines cake mix (dark chocolate is my favorite) but just get whatever flavor you like the best because thats the part your baby wont care about, because the cake is for everyone at the party, right? okay.
what i do is, i take the duncan hines mix and do milk (sometimes buttermilk) in lieu of water and sometimes butter instead of oil, but i like the oil if its all natural. i put the called for amount of eggs then bake it for the MINIMUM amount of time the box says, and your cake will be moist and delicious! and easy, because its just a box mix!
oh and some suggestions are;
if there are a lot of kids at the party, maybe do a white cake with light and fluffy frosting (kids shouldnt have really rich stuff when they are running around playing because their tummies are sensitive)
if there are lots of women, do chocolate! (we love chocolate what can i say! red velvet or dark chocolate is good too, with any kind of frosting)
if there are lots of men then do carrot cake. (ive noticed a lot of men like carrot or spiced cake, and sometimes fruit flavored, with cream cheese frosting)
good luck! and most of all HAVE FUN