http://revach.net/article.php?id=3622

Section: Moadim   Category: Hagadah Shel Pesach
SheEino Yodei'a Lishol - What Do We Want From Such Little Kids?

On pesach every child needs to be involved so we do all sorts of extraordinary things that we don't do during the year just so the children ask.  And if they are too little to comprehend these changes or don't have the capacity to open their mouths and ask "At P'sach Lo", we put the questions in their mouths.  If they are too young to make even this minimum effort of asking, why do we bother with them at all?  Even for Chinuch the children need to be old enough to participate in the mitzva.  Why not wait until next year when they develop and mature?

The Otzar Divrei HaMeforshim brings from Rav Moshe Rappaport of Keidan that we insist on their participation since many of the harshest decrees in Mitzrayim were directed towards these young children and many of the miracles were to save them.  He lists seven decrees.

1.  Husbands and their wives were separate to prevent children from being born
2.  A baby boy was killed during delivery
3.  The boys were thrown into the river
4.  They plastered the children into the building walls
5.  They were slaughtered to let Paroh bathe in their blood to cure his Tzora'as
6.  They were thrown into the iron melting pot
7.  The mother's miscarried while assisting their husbands in making the bricks for building

 Just like we use the rule that women are obligated in a Mitzva where they were part of the Nes, so too these little children are very much a part of Pesach and we help them if they are unable to help themselves.