I have a friend that have a girl from a previous marriage. When she re-married, her husband involved her daughter in such a beautifull way. After her dad gave the bride to her new husband at the altar (the girl was walking infront of her mother) they "stopped" there and the guy gave the girl a necklace with a pendant on (he went down on one knee to put it around her neck, she was 8 years old) and sort of made her a promise that he would love her, care for her and be there for her just like he will love and care for her mother, because from that day they are a family. I know it's not the same with you guys, because they are YOUR kids and they are a tad younger, but it was soooo beautifull the way he inluded her in his promise to his wife, I just had to share.

I actually have no idea how you could incorperate them. They are a bit to young to be flowergirls or make toasts :P How about ... nothing ... ... ... .. I'll have to really think of something. If I come up with something, I'll post

ETA: I like the christening idea