Check out the Obrien Hooky available in the 110 and 118:
http://www.obrien.com/product/hooky/ and the Jr. Nomads available in white or black only:
http://www.obrien.com/product/nomad-black/
Rad thing about the Hooky is it's built from the ground up for kids... not another bulky thick foam board. The majority of the tip and tail of the board are constructed from the DuraRail material so when they're dragging the board on the dock or drop it int he garage or parking lot it's not going to split and allow water to compromise the core. Jr. Nomads are built to the same standards as the adult bindings and feature a 5* canting in the base for increased board control.
-Cheers!