Lots of info here http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=102
I'd grow some Paperwhite narcissus in water, as they only take about 6 weeks from start to flowering and you can virtually watch them grow, and the children can see the roots as well as the flowers, and they don't have to be started off in the cold and dark like hyacinths, so the children will remain engaged with the process.
Paperwhites are also better than hyacinths for using with children as hyacinth bulbs can irritate sensitive skin and cause a nasty rash.
Some little blue muscari or scillas in a shallow bowl of compost would be lovely, and I remember growing bowls of crocuses as a child, but these really need keeping outside in the cool untll the flowerbuds have formed - then you can bring them indoors.
And of course, a big Amaryllis bulb with it's dramatic bloom has fantastic Wow! factor.
What a lovely project - enjoy