Step 1: Materials & tools
light switch (thicker ones work better)
wire coat hanger (thicker/stiffer ones work better for this, too)
wooden dowel or bead ~ 1/2" diameter
hot glue gun
Step 2: Make the push-pull toggle
Step 3: Prepare the switch
Remove the light switch plate cover thingy. Remove the light switch. Disconnect the wires, but remember where they go before you do.
Drill a hole in the switch that is slightly larger than the diameter of the coat hanger wire, just like the bead. You can do it either top-to-bottom or side-to-side. I've done both, and side-to-side worked a little better for me.
Reconnect the wires to the same points. Reinstall the light switch. Replace the light switch plate cover thingy.
You may now turn the circuit back on.
Step 4: Assemble the parts
Unwind the coat hanger and straighten it out. Measure the distance between the light switch and how high your kids can reach. Add an inch or so for each end to attach to the switch and to the bead, and cut that length of coat hanger.
Run one end of the hanger through the bead and wrap it around to hold the bead in place. If you want, a bit of hot glue can cover the end of the wire, to protect little hands.
Run the other end through the hole in the light switch and wrap the coat hanger around there. Again. a bit of hot glue might be in order to cover the end of the wire.
Step 5: Sit back while your kids turn on their own light.
I said a side-to-side hole worked better above, because when the wire is pushed up that works better. Top-to-bottom also works, if you've done a good job wrapping the wire tightly around the switch.