My first thought was the same as Eliza's. I took my 3 yr old shopping for a gift for the baby. He was so excited! He'd decided that babies like rattles, but when we got to the store, he picked out a shockingly orange sleeper with a robot on it. Not my first choice, but I love that it is coming from him.
My mother, on the other hand, decided to make my two boys "big brother gifts." She had some fabric and made them blankets. They LOVE blankets, so they'll love those. I think it's great that they're coming from someone other than me! When #2 was born, my sister sent a little toy to my #1. Honestly, it was great that he had something to do in the boring hospital room after his 2-yr-old attention span ran dry. But it wasn't really that special of a thing for him. Of course, your kids are older.
I don't see a problem with the baby getting all the attention. I mean, your kids get all the attention on their birthdays, right? Besides, kids need to learn that it's not always about them, and to be happy for and contribute to other peoples' special days. I think your kids are old enough do handle that.
Oh, and as for feeling special themselves, make sure that you let them hold the baby and take pictures of them, praise them for being good big siblings. And spend a few minutes with them while visitors are holding the baby, etc. They'll know that the baby didn't just steal their mom!