Another strong vote for the Pittwater Junior (PJ) above.
Self draining, simple rig with an open transom to let kids get back in easily.
I taught a group of kids to sail in them and compared to other classes, they had a ball.
So easy to right that we actually had to tell the kids they had to do some sailing before they were allowed to muck around capsizing them.
And unlike an Opi, there's room for a friend too.
Those who brought Opi's and Sabots along to a training session were a nightmare to manage by comparison as real beginners often needed help to right and bail the boat and would take up way more time to look after and often scare the kids out of them.
The Bic can be good fun, but doesn't steer and sail nearly as well.
I am a fan of the MJ and there are self draining versions, but the flapping jib will scare a young inexperienced kids witless before they even leave the beach.
For what you say you want, the PJ is the go.
There were a lot of them around BYRA on Pittwater a decade ago. Not sure what its like now.
This seems to be a club that uses them. Lots of pictures on the site
www.callalajuniorsailingschool.org/mynews.html