H.H.
Sounds like you've already done a great job of getting them excited about the new baby! I always had gifts from the baby to big brother and/or big sister....something they're interested in. For example: Thomas the train, Geo Tracks, and Transformers were huge hits for my son. My daughter loved the "dress-up" clothes and Elmo books she got. So basically just find something special for the older siblings, since they've made so much for the new addition. Best of luck!