Yearly photos w/ interests noted. Make up a few pages in photoshop or an editing program of choice, and create a printed 8x10 book. Give to your children when they graduate as a gift...I would use a few head shots and definitely lifestyle candid shots to get the real feel of what they were like at each age.
Great idea for a party invitation...child holding chalkboard with invite info.
We used frames in our last family picture day. It was a little challenging with Branigan, but once we just let her decide how to use them, rather than trying to pose them, it turned out really neat. Would recommend trying this, the pictures were great!