I'm going to have to go against the popular opinion here, I think. I totally agree with you, T.. It should be a special day for the birthday girl. Kids are not taught that it's not "all about them" all the time and society is paying for it. Part of loving your children is teaching them how to get along in the world and how to be polite and well mannered.
I don't see anything wrong with giving your older child a goody bag just like you'd give to any other child at the party, but presents are for the birthday child. Just explain to your two year old that it's her sister's birthday and therefore she gets the presents, but her birthday will be next and it will be her turn to get presents. Don't underestimate how much a two year old can understand - I think they can grasp that concept very well. All siblings are jealous of each other at times. Take the opportunity to teach them about sharing and graciousness.
At my three year old nephew's birthday, all the invited party children insisted on unwrapping his gifts while he was unwrapping them and once unwrapped, the "guests" took the presents and started playing with them (before the birthday boy could play with then, not with the birthday boy). Only one parent corrected any of their bad mannered children. Don't get me wrong, I LOVE kids (mine are grown, now I have grandkids), but it is not any fun being around bad behaved, rude children.